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EXECUTIVE LETTER 

Dear Colleagues, 

Air travel continues to be the safest means of transportation, but that does not allow for us to 

become complacent. We continually strive for improvements in our industry safety record, which is 

a testament to our ongoing commitment to safety. 

Fatigue Risk Management Systems (FRMS) continues the move from prescriptive to performance 

based regulatory oversight. As in Safety Management Systems (SMS), FRMS strives to find the 

realistic balance between safety, productivity and costs in an organization, through collection of 

data and a formal assessment of risk. 

Traditionally, crewmember fatigue has been managed through prescribed limits on maximum flight 

and duty hours, based on a historical understanding of fatigue through simple work and rest period 

relationships. New knowledge related to the effects of sleep and circadian rhythms provides an 

additional dimension to the management of fatigue risks. An FRMS provides a means of adding 

this safety dimension, allowing operators to work both safer and more efficiently. 

This FRMS Implementation Guide for Operators is a significant milestone. It marks the successful 

collaboration between IATA, IFALPA and ICAO to jointly lead and serve industry in the ongoing 

development of fatigue management, using the most current science. The input of these three 

organizations has ensured that this document presents a scientifically-based approach that is 

widely acceptable to the operators and the crew members who will be using it. It also offers this 

information in an accessible and practical way to assist implementation. 

We are extremely proud to mutually introduce this FRMS Implementation Guide for Operators, 

which will contribute to the improved management of fatigue risk, and to ultimately achieve our 

common goal of improving aviation safety worldwide. 

Guenther Matschnigg 

Senior Vice President 

Safety, Operations & 

Infrastructure, IATA 

Nancy Graham 

Director 

Air Navigation Bureau 

ICAO

Don Wykoff 

President 

International Federation of 

Air Line Pilots’ Associations 
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DISCLAIMER 

The information contained in this publication is subject to constant review in the light of changing 

government requirements and regulations. No subscriber or other reader should act on the basis of 

any such information without referring to applicable laws and regulations and without taking 

appropriate professional advice. Although every effort has been made to ensure accuracy, the 

International Air Transport Association (IATA), the International Civil Aviation Organization (ICAO), 

the International Federation of Airline Pilots’ Associations (IFALPA), and other contributors to this 

publication shall not be held responsible for any loss or damage caused by errors, omissions, 

misprints or misinterpretation of the contents hereof. Furthermore, the International Air Transport 

Association, the International Civil Aviation Organization, the International Federation of Airline 

Pilots’ Associations, and the contributors to this publication expressly disclaim any and all liability to 

any person or entity, whether a purchaser of this publication or not, in respect of anything done or 

omitted, and the consequences of anything done or omitted, by any such person or entity in 

reliance on the contents of this publication. 

Opinions expressed in this publication do not necessarily reflect the opinion of the International Air 

Transport Association, International Civil Aviation Organization, nor the International Federation of 

Airline Pilots’ Associations. The mention of specific companies, products in this publication does 

not imply that they are endorsed or recommended by the any of the above in preference to others 

of a similar nature which are not mentioned. 

No part of this publication may be reproduced, recast, reformatted or transmitted in any form by any 

means, electronic or mechanical, including photocopying, recording or any information storage and 

retrieval system, without the prior written permission of the authors. 
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TABLE OF CONTENTS 

1.0 INTRODUCTION TO FRMS................................................................................................................... 1

1.1 WHAT IS A FATIGUE RISK MANAGEMENT SYSTEM?........................................................................... 1

1.2 WHY THE AVIATION INDUSTRY IS INTRODUCING FRMS..................................................................... 2

1.3 ICAO REQUIREMENTS FOR FATIGUE RISK MANAGEMENT SYSTEMS.................................................. 3

1.4 STRUCTURE OF THIS MANUAL ......................................................................................................... 6

2.0 SCIENCE FOR FRMS............................................................................................................................ 1

2.1 INTRODUCTION............................................................................................................................... 1

2.2 ESSENTIAL SLEEP SCIENCE ............................................................................................................ 1

2.2.1 What is Happening in the Brain During Sleep................................................................... 1

2.2.2 The Issue of Sleep Quality ................................................................................................ 5

2.2.3 Consequences of Not Getting Enough Sleep.................................................................... 7

2.3 INTRODUCTION TO CIRCADIAN RHYTHMS ....................................................................................... 10

2.3.1 Examples of Circadian Rhythm ....................................................................................... 10

2.3.2 The Circadian Body Clock and Sleep.............................................................................. 12

2.3.3 3 Sensitivity of the Circadian Body Clock to Light........................................................... 14

2.3.4 Shift Work ........................................................................................................................ 15

2.3.5 Jet Lag............................................................................................................................. 17

2.4 SUMMARY OF ESSENTIAL SCIENCE FOR FRMS.............................................................................. 20

3.0 FRMS POLICY AND DOCUMENTATION............................................................................................. 1

3.2 FRMS POLICY ............................................................................................................................... 3

3.2.1 Scope of the FRMS ........................................................................................................... 3

3.2.2 Things that the FRMS Policy Must Cover ......................................................................... 4

3.3 EXAMPLES OF FRMS POLICY STATEMENTS..................................................................................... 6

3.3.1 FRMS Policy Statement for a Major Air Carrier................................................................. 6

3.3.2 FRMS Policy Statement for a Small Operator Providing Medical Evacuation Services ... 7

3.4 FRMS DOCUMENTATION ................................................................................................................ 8

3.4.1 Example of Terms of Reference for a Fatigue Safety Action Group................................. 9

4.0 FATIGUE RISK MANAGEMENT (FRM) PROCESSES ........................................................................ 1

4.1 INTRODUCTION TO FRM PROCESSES .............................................................................................. 1

4.2 FRM PROCESSES STEP 1: IDENTIFY THE OPERATIONS COVERED..................................................... 5

4.3 FRM PROCESSES STEP 2: GATHER DATA AND INFORMATION........................................................... 5

4.4 FRM PROCESSES STEP 3: HAZARD IDENTIFICATION ........................................................................ 8

4.4.1 Predictive Hazard Identification Processes ....................................................................... 8

4.4.2 Proactive Hazard Identification Processes...................................................................... 11

4.4.3 Reactive Hazard Identification Processes....................................................................... 18

4.5 FRM PROCESSES STEP 4: RISK ASSESSMENT .............................................................................. 19

4.6 FRM PROCESSES STEP 5: RISK MITIGATION ................................................................................. 21

4.7 EXAMPLE: SETTING UP FRM PROCESSES FOR A NEW ULR ROUTE................................................ 24

4.7.1 Step 1 – Identify the Operation........................................................................................ 24

4.7.2 Step 2 – Gather Data and Information ............................................................................ 24

4.7.3 Step 3 – Identify Hazards ................................................................................................ 26

4.7.4 Step 4 – Assess Safety Risk ........................................................................................... 27

4.7.5 Step 5 – Select and Implement Controls and Mitigations ............................................... 27
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4.7.6 Step 6 – Monitor Effectiveness of Controls and Mitigations............................................ 28

4.7.7 Linking to FRMS Safety Assurance Processes............................................................... 28

5.0 FRMS SAFETY ASSURANCE PROCESSES....................................................................................... 1

5.1 INTRODUCTION TO FRMS SAFETY ASSURANCE PROCESSES............................................................ 1

5.2 FRMS SAFETY ASSURANCE PROCESSES STEP 1: COLLECT AND REVIEW DATA................................ 5

5.3 FRMS SAFETY ASSURANCE PROCESSES STEP 2: EVALUATE FRMS PERFORMANCE........................ 7

5.4 FRMS SAFETY ASSURANCE PROCESSES STEP 3: IDENTIFY EMERGING HAZARDS............................. 9

5.5 FRMS SAFETY ASSURANCE PROCESSES STEP 4: IDENTIFY CHANGES AFFECTING FRMS ................ 9

5.6 FRMS SAFETY ASSURANCE PROCESSES STEP 5: IMPROVE EFFECTIVENESS OF FRMS.................. 10

5.7 ASSIGNING RESPONSIBILITY FOR FRMS SAFETY ASSURANCE PROCESSES .................................... 10

5.8 EXAMPLES OF FRMS SAFETY ASSURANCE PROCESSES INTERACTING WITH FRM PROCESSES ...... 11

6.0 FRMS PROMOTION PROCESSES ...................................................................................................... 1

6.1 INTRODUCTION TO FRMS PROMOTION PROCESSES ........................................................................ 1

6.2 FRMS TRAINING PROGRAMS.......................................................................................................... 2

6.2.1 Who Needs to be Trained ................................................................................................. 2

6.2.2 Curriculum ......................................................................................................................... 2

6.2.3 FRMS Training Formats and Frequency........................................................................... 6

6.2.4 FRMS Training Evaluation ................................................................................................ 7

6.2.5 FRMS Training Documentation......................................................................................... 8

6.2.6 FRMS Communications Plan ............................................................................................ 8

7.0 FRMS IMPLEMENTATION.................................................................................................................... 1

7.1 INTRODUCTION TO FRMS IMPLEMENTATION .................................................................................... 1

7.2 PHASE I: PLANNING........................................................................................................................ 2

7.3 PHASE II: IMPLEMENT REACTIVE FRM PROCESSES ......................................................................... 3

7.5 PHASE IV: IMPLEMENT FRMS SAFETY ASSURANCE PROCESSES ..................................................... 4

7.6 OPERATIONAL EXAMPLE OF STAGED FRMS IMPLEMENTATION ......................................................... 5

APPENDIX A: GLOSSARY ...................................................................................................................... 1

APPENDIX B: MEASURING CREWMEMBER FATIGUE........................................................................ 1

B1 CREWMEMBERS’ RECALL OF FATIGUE ............................................................................................. 1

B1.1 Fatigue Reporting Forms................................................................................................... 1

B1.2 Retrospective Surveys ...................................................................................................... 3

B2 MONITORING CREWMEMBER FATIGUE DURING FLIGHT OPERATIONS ................................................ 5

B2.1 Subjective Fatigue and Sleepiness Ratings...................................................................... 5

B2.2 Objective Performance Measurement............................................................................... 9

B2.3 Monitoring Sleep.............................................................................................................. 11

B2.4 Monitoring the Circadian Body Clock Cycle .................................................................... 19

B3 EVALUATING THE CONTRIBUTION OF FATIGUE TO SAFETY EVENTS ................................................. 21

APPENDIX C: PROCEDURES FOR CONTROLLED REST ON THE FLIGHT DECK............................ 1
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1.0 INTRODUCTION TO FRMS 

The purpose of this FRMS Implementation Guide is to provide air operators with information for 

implementing an FRMS that is consistent with ICAO Standards and Recommended Practices 

(SARPs). As the ICAO provisions for FRMS evolve, every effort will be made to keep this manual 

up to date. However, it is recommended that operators check the current SARPs to find out if 

anything important has changed since this version of the manual was developed. Operators also 

need to ensure that their FRMS meets the requirements of their State’s regulatory authority. 

A variety of options to address the ICAO Standards for an FRMS are presented throughout this 

guide. These can be adapted to the needs of different sizes and types of operators (international, 

domestic, passenger, cargo, etc) and to specific operations (Ultra-Long Range (ULR), long haul, 

short haul domestic, on-call/charter, etc). It is not necessary to implement all of these options to 

have an effective FRMS that meets regulatory requirements. 

1.1 WHAT IS A FATIGUE RISK MANAGEMENT SYSTEM? 

Crewmember fatigue can be defined as: 

A physiological state of reduced mental or physical performance capability resulting from 

sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical 

activity) that can impair a crew member’s alertness and ability to safely operate an aircraft or 

perform safety related duties. 

Fatigue is a major human factors hazard because it affects most aspects of a crewmember’s 

ability to do their job. It therefore has implications for safety. ICAO defines a Fatigue Risk 

Management System (FRMS) as: 

A data-driven means of continuously monitoring and managing fatigue-related safety risks, 

based upon scientific principles and knowledge as well as operational experience that aims 

to ensure relevant personnel are performing at adequate levels of alertness. 

An FRMS aims to ensure that flight and cabin crew members are sufficiently alert so they 

can operate to a satisfactory level of performance. It applies principles and processes from 

Safety Management Systems (SMS)1

 to manage the specific risks associated with 

crewmember fatigue. Like SMS, FRMS seeks to achieve a realistic balance between safety, 

productivity, and costs. It seeks to proactively identify opportunities to improve operational 

processes and reduce risk, as well as identifying deficiencies after adverse events. The 

structure of an FRMS as described here is modelled on the SMS framework. The core 

activities are safety risk management (described in the SARPS as FRM processes) and 

safety assurance (described in the SARPs as FRMS safety assurance processes). These 

core activities are governed by an FRMS policy and supported by FRMS promotion 

processes, and the system must be documented. 

Both SMS and FRMS rely on the concept of an ‘effective safety reporting culture’1

 ,where 

personnel have been trained and are constantly encouraged to report hazards whenever 

observed in the operating environment. To encourage the reporting of fatigue hazards by all 

personnel involved in an FRMS, an operator must clearly distinguish between: 

• Unintentional human errors, which are accepted as a normal part of human behaviour 

and are recognized and managed within the FRMS; and 

• Deliberate violations of rules and established procedures. An operator should have 

processes independent of the FRMS to deal with intentional non-compliance 

 

1

 See ICAO Safety Management Manual (Doc 9859) and IATA Introduction to Safety Management Systems (SMS), 

2nd Edition. 
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1.2 WHY THE AVIATION INDUSTRY IS INTRODUCING FRMS 

The traditional regulatory approach to managing crewmember fatigue has been to prescribe 

limits on maximum daily, monthly, and yearly flight and duty hours, and require minimum 

breaks within and between duty periods. This approach comes from a long history of limits 

on working hours dating back to the industrial revolution. It entered the transportation sector 

in the early 20th century in a series of regulations that limited working hours in rail, road and 

aviation operations2

. The approach reflects early understanding that long unbroken periods 

of work could produce fatigue (now known as ‘time-on-task’ fatigue), and that sufficient time 

is needed to recover from work demands and to attend to non-work aspects of life. 

In the second half of the 20th century, scientific evidence began accumulating that implicated 

other causes of fatigue in addition to time-on-task, particularly in 24/7 operations. The most 

significant new understanding concerns: 

• The vital importance of adequate sleep (not just rest) for restoring and maintaining all 

aspects of waking function; and 

• Daily rhythms in the ability to perform mental and physical work, and in sleep propensity 

(the ability to fall asleep and stay asleep), that are driven by the daily cycle of the 

circadian biological clock in the brain. 

This new knowledge is particularly relevant in the aviation industry which is unique in 

combining 24/7 operations with trans-meridian flight. 

In parallel, understanding of human error and its role in accident causation has increased. 

Typically, accidents and incidents result from interactions between organizational processes 

(i.e. workplace conditions that lead crewmembers to commit active failures), and latent 

conditions that can penetrate current defenses and have adverse effects on safety1

. The 

FRMS approach is designed to apply this new knowledge from fatigue science and safety 

science. It is intended to provide an equivalent, or enhanced, level of safety, while also 

offering greater operational flexibility. 

Prescriptive flight and duty time limits represent a somewhat simplistic view of safety – being 

inside the limits is safe while being outside the limits is unsafe – and they represent a single 

defensive strategy. While they are adequate for some types of operations, they are a onesize-fits-all approach that does not take into account operational differences or differences 

among crewmembers. 

In contrast, an FRMS employs multi-layered defensive strategies to manage fatigue-related 

risks regardless of their source. It includes data-driven, ongoing adaptive processes that can 

identify fatigue hazards and then develop, implement and evaluate controls and mitigation 

strategies. These include both organizational and personal mitigation strategies. However, 

the cost and complexity of an FRMS may not be justified for operations that remain inside 

the flight and duty time limits and where fatigue-related risk is low. Some operators may 

therefore choose to place only certain parts of their operations under an FRMS or not 

implement an FRMS at all. Nonetheless, where an FRMS is not implemented, it remains the 

operator’s responsibility to manage fatigue-related risks through their existing safety 

management processes. 

 

2

 Gander PH, Hartley L, Powell D, Cabon P, Hitchcock E, Mills A. Popkin S (2010). Fatigue risk management I: 

organizational factors. Accident Analysis and Prevention 43:573-590 
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Like SMS, FRMS represents a performance-based regulatory approach (in contrast to the 

prescriptive regulatory approach of flight and duty time limits). In essence, this means that 

FRMS regulations define requirements for operators to manage fatigue risk, rather than 

prescribing limits that cannot consider aspects specific to the organization or operating 

environment. The Fatigue Management SARPs (Annex 6, Part I and Appendix 8) prescribe 

components that must be in an FRMS, and the ICAO guidance material provides further 

information on how an FRMS should function. 

1.3 ICAO REQUIREMENTS FOR FATIGUE RISK MANAGEMENT SYSTEMS

This section describes the Standards and Recommended Practices (SARPs) relating to the 

management of fatigue experienced by flight and cabin crew. These SARPs provide the 

high-level regulatory framework for both prescriptive flight and duty limitations and FRMS as 

methods for managing fatigue risk. Both methods share two important basic features: 

1. They are required to take into consideration the dynamics of transient and cumulative 

sleep loss and recovery, the circadian biological clock, and the impact of workload on 

fatigue, along with operational requirements. 

2. Because fatigue is affected by all waking activities not only work demands, regulations 

for both are necessarily predicated on the need for shared responsibility between the 

operator and individual crewmembers for its management. So, whether complying with 

prescriptive flight and duty limitations or using and FRMS, operators are responsible for 

providing schedules that allow crewmembers to perform at adequate levels of alertness 

and crewmembers are responsible for using that time to start work well-rested. The 

requirement for shared responsibility in relation to FRMS is discussed further in Chapter 

Three. 

FRMS also shares the building blocks of SMS. This means that an FRMS is predicated on: 

effective safety reporting; senior management commitment; a process of continuous 

monitoring; a process for investigation of safety occurrences that aims to identify safety 

deficiencies rather than apportioning blame; the sharing of information and best practices; 

integrated training for operational personnel; effective implementation of standard operating 

procedures (SOPs); and a commitment to continuous improvement. So, together, the 

foundations of prescriptive flight and duty time limitations and SMS form the building blocks 

of FRMS (see Table 1). 

Table 1 – FRMS Building Blocks 

FRMS Building Blocks 

Prescriptive flight and duty time limitations • Addresses transient and cumulative 

fatigue 

• Shared operator-individual 

responsibility 

SMS • Effective safety reporting 

• Senior management commitment 

• Continuous monitoring process 

• Investigation of safety occurrences 

• Sharing of information 

• Integrated training 

• Effective implementation of SOPs 

• Continuous improvement 
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However, an FRMS, as a management system focused on fatigue, also has added 

requirements beyond that which would be expected of an operator complying with 

prescriptive flight and duty time limitations and managing their fatigue risks through their 

SMS. In meeting these additional FRMS-specific requirements, an operator with an 

approved FRMS may move outside the prescribed limits. Therefore, the fatigue 

management SARPs in Section 4.10, Annex 6, Part I, and include particular Standards that 

enable the effective regulation of FRMS. 

The following text box contains the SARPs in Annex 6 Part I that relate to Fatigue 

Management. States are required to have regulations for prescriptive flight and duty time 

limitations, but they also have the option to establish FRMS regulations. In addition, there is 

a requirement that when FRMS is used, operations manuals reflect the FRMS option (Annex 

6, Part I, Appendix 2). 

Appendix 8 has been added to Annex 6, Part I to give detailed requirements for an FRMS 

which must include, at a minimum, the following components. 

1. FRMS policy and documentation; 

2. Fatigue risk management processes; 

3. FRMS safety assurance processes; and 

4. FRMS promotion processes. 

Table 1.1 shows how these components map to the requirements of SMS. 

See Example 1 to view Annex 6, Part 1, which recommends “where an operator has an 

FRMS, it is integrated with the operator’s SMS.” 
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Example 1 – Annex 6 Part I – 4.10 Fatigue Management 

4.10.1 The State of the Operator shall establish regulations for the purpose of managing fatigue. These 

regulations shall be based upon scientific principles and knowledge, with the aim of ensuring that flight 

and cabin crew members are performing at an adequate level of alertness. Accordingly, the State of the 

Operator shall establish: 

a) regulations for flight time, flight duty period, duty period and rest period limitations; and 

b) where authorizing an operator to use a Fatigue Risk Management System (FRMS) to manage 

fatigue, FRMS regulations. 

4.10.2 The State of the Operator shall require that the operator, in compliance with 4.10.1 and for the purposes 

of managing its fatigue-related safety risks, establish either: 

a) flight time, flight duty period, duty period and rest period limitation that are within the prescriptive 

fatigue management regulations established by the State of the Operator; or 

b) a Fatigue Risk Management System (FRMS) in compliance with 4.10.6 for all operations; or 

c) an FRMS in compliance with 4.10.6 for part of its operations and the requirements of 4.10.2 a) for the 

remainder of its operations. 

4.10.3 Where the operator adopts prescriptive fatigue management regulations for part or all of its operations, 

the State of the Operator may approve, in exceptional circumstances, variations to these regulations on 

the basis of a risk assessment provided by the operator. Approved variations shall provide a level of 

safety equivalent to, or better than, that achieved through the prescriptive fatigue management 

regulations. 

4.10.4 The State of the Operator shall approve an operator’s FRMS before it may take the place of any or all of 

the prescriptive fatigue management regulations. An approved FRMS shall provide a level of safety 

equivalent to, or better than, the prescriptive fatigue management regulations. 

4.10.5 States that approve an operator’s FRMS shall establish a process to ensure that an FRMS provides a 

level of safety equivalent to, or better than, the prescriptive fatigue management regulations. As part of 

this process, the State of the Operator shall: 

a) require that the operator establish maximum values for flight times and/or flight duty periods(s) and 

duty period(s), and minimum values for rest periods. These values shall be based upon scientific 

principles and knowledge, subject to safety assurance processes, and acceptable to the State of the 

Operator; 

b) mandate a decrease in maximum values and an increase in minimum values in the event that the 

operator’s data indicates these values are too high or too low, respectively; and 

c) approve any increase in maximum values or decrease in minimum values only after evaluating the 

operator’s justification for such changes, based on accumulated FRMS experience and fatiguerelated data. 

4.10.6 Where an operator implements an FRMS to manage fatigue-related safety risks, the operator shall, as a 

minimum: 

a) incorporate scientific principles and knowledge within the FRMS; 

b) identify fatigue-related safety hazards and the resulting risks on an ongoing basis; 

c) ensure that remedial actions, necessary to effectively mitigate the risks associated with the hazards, 

are implemented promptly; 

d) provide for continuous monitoring and regular assessment of the mitigation of fatigue risks achieved 

by such actions; and 

e) provide for continuous improvement to the overall performance of the FRMS. 

4.10.7 Recommendation.— States should require that, where an operator has an FRMS, it is integrated with 

the operator’s SMS. 

4.10.8 An operator shall maintain records for all its flight and cabin crew members of flight time, flight duty 

periods, duty periods, and rest periods for a period of time specified by the State of the Operator.
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Table 1.1 Comparing SMS and FRMS Components 

SMS Framework FRMS 

1. Safety policy and objectives 1. FRMS policy and documentation 

2. Safety risk management 2. FRM processes 

• Identification of hazards 

• Risk assessment 

• Risk mitigation 

3. Safety assurance 3. FRMS safety assurance processes 

• FRMS performance monitoring 

• Management of operational and 

organisational change 

• Continuous FRMS improvement 

4. Safety promotion 4. FRMS promotion processes 

• Training programs 

• FRMS communication plan 

The core operational activities of the FRMS are the FRM processes and the FRMS safety 

assurance processes. They are supported by organizational arrangements defined in the 

FRMS policy and documentation, and by the FRMS promotion processes. 

1.4 STRUCTURE OF THIS MANUAL

Figure 1.1 shows a basic framework linking the required components of an FRMS. For ease 

of explanation, Figure 1.1 presents a single, central, functional group, designated as the 

“Fatigue Safety Action Group”, responsible for all of these FRMS components. The Fatigue 

Safety Action Group includes representatives of all stakeholder groups (management, 

scheduling, and crewmembers) and other individuals as needed to ensure that it has 

appropriate access to scientific and medical expertise. However, depending on the 

organizational structure, some of the Fatigue Safety Action Group functions as described in 

this manual may be undertaken by other groups within the organization (discussed further in 

Chapter 3). The important thing is that, irrespective of who does them, all of the component 

functions required under an FRMS be performed. 
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Figure 1.1: Linking the required components of an FRMS 

Communication between the FRMS processes and the SMS (in both directions) is necessary to 

integrate the management of the fatigue risks into the broader risk management activities of the 

SMS. 

The detailed structure of an FRMS, and the specific ways in which it links to an operator’s SMS, will 

vary according to: 

• the size of the organization; 

• the type and complexity of the operations being managed; 

• the relative maturity of the FRMS and the SMS; and 

• the relative importance of the fatigue hazards. 

The FRMS approach is based on applying scientific principles and knowledge to manage 

crewmember fatigue. Chapter Two introduces the essential scientific concepts that are needed to 

develop and implement an FRMS. Chapters Three, Four, Five, and Six each deal with one of the 

required FRMS components. Chapter Seven steps though a staged approach for implementing an 

FRMS. 

Appendices A, B and C provide extra information to support that provided in the preceding 

chapters. For ease of reference, Appendix A provides a glossary of terms used in this manual. 

Appendix B provides more detailed information on methods of measuring fatigue as part of the 

FRM processes presented in Chapter Three. Appendix C also supports Chapter Three by 

providing further information on the use of controlled rest on the flight deck as a mitigator of fatigue 

risk.
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2.0 SCIENCE FOR FRMS 

2.1 INTRODUCTION

The FRMS approach represents an opportunity for operators to use advances in scientific 

knowledge to improve safety and increase operational flexibility. This chapter reviews the 

scientific principles needed to develop and implement an effective FRMS. 

In Chapter One, the ICAO definition of crewmember fatigue was given as: 

A physiological state of reduced mental or physical performance capability resulting from 

sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical 

activity) that can impair a crew member’s alertness and ability to safely operate an aircraft or 

perform safety related duties. 

In flight operations, fatigue can be measured either subjectively by having crewmembers rate 

how they feel, or objectively by measuring crewmembers’ performance (Chapter Four and 

Appendix B). 

Another way of thinking about this is that fatigue is a state that results from an imbalance 

between: 

• The physical and mental exertion of all waking activities (not only duty demands); and 

• Recovery from that exertion, which (except for recovery from muscle fatigue) requires 

sleep. 

Following this line of thinking, to reduce crewmember fatigue requires reducing the exertion 

of waking activities and/or improving sleep. Two areas of science are central to this and are 

the focus of this Chapter. 

1. Sleep science – particularly the effects of not getting enough sleep (on one night or 

across multiple nights), and how to recover from them; and 

2. Circadian rhythms – the study of innate rhythms driven by the daily cycle of the 

circadian biological clock (a pacemaker in the brain). These include: 

a) Rhythms in subjective feelings of fatigue and sleepiness; and 

b) Rhythms in the ability to perform mental and physical work, which affect the effort 

required to reach an acceptable level of performance (exertion); and 

c) Rhythms in sleep propensity (the ability to fall asleep and stay asleep), which affect 

recovery. 

2.2 ESSENTIAL SLEEP SCIENCE

There is a widespread belief that sleep time can be traded off to increase the amount of time 

available for waking activities in a busy lifestyle. Sleep science makes it very clear that sleep 

is not a tradable commodity. 

2.2.1 What is Happening in the Brain During Sleep 

There are a variety of ways of looking at what is happening in the sleeping brain, 

from reflecting on dreams to using advanced medical imaging techniques. 

Currently, the most common research method is known as polysomnography (see 

Appendix B for details). This involves sticking removable electrodes to the scalp 

and face and connecting them to a recording device, to measure three different 

types of electrical activity: 1) brainwaves (electroencephalogram or EEG); 2) eye 

movements (electroculogram or EOG); and 3) muscle tone (electromyogram or 

EMG). Using polysomnography, it is possible to identify two very different kinds of 

sleep. 
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Non-Rapid Eye Movement Sleep 

Compared to waking brain activity, non-Rapid Eye Movement sleep (non-REM 

sleep) involves gradual slowing of the brainwaves. The amplitude (height) of the 

brainwaves also becomes larger as the electrical activity of large numbers of brain 

cells (neurons) becomes synchronized so that they fire in unison. Heart rate and 

breathing tend to be slow and regular. 

People woken from non-REM sleep do not usually recall much mental activity. 

However, it is still possible for the body to move in response to instructions from 

the brain. Because of these features, non-REM sleep is sometimes described as 

‘a relatively inactive brain in a movable body’. 

Non-REM sleep is usually divided into 4 stages, based on the characteristics of the 

brainwaves. 

• Stages 1 and 2 represent lighter sleep (it is not very difficult to wake someone 

up). It is usual to enter sleep through Stage 1 and then Stage 2 non-REM. 

• Stages 3 and 4 represent deeper sleep (it can be very hard to wake someone 

up). Stages 3 and 4 are characterized by high amplitude slow brainwaves, 

and are together often described as slow-wave sleep (or deep sleep). 

Slow-wave sleep has a number of important properties. Pressure for slow-wave 

sleep builds up across waking and discharges across sleep. In other words: 

• The longer you are awake, the more slow-wave sleep you will have in your 

next sleep period; and 

• Across a sleep period, the proportion of time spent in slow-wave sleep 

decreases. 

This rising and falling of pressure for slow wave sleep is sometimes called the 

sleep homeostatic process, and it is a component in most of the biomathematical models that are used to predict crewmember fatigue levels (see 

Chapter Four). 

Even in slow-wave sleep, the brain is still about 80% activated and capable of 

active cognitive processing. There is growing evidence that slow-wave sleep is 

essential for the consolidation of some types of memory, and is therefore 

necessary for learning. 

Operational Note: 

Mitigation Strategies for Sleep Inertia

Operationally, slow-wave sleep may be important because the brain can have 

difficulty transitioning out of it when someone is woken up suddenly. This is known 

as sleep inertia – feelings of grogginess and disorientation, with impaired shortterm memory and decision-making. Sleep inertia can occur coming out of lighter 

sleep, but it tends to be longer and more disorienting when someone is woken 

abruptly out of slow-wave sleep. This is sometimes used as an argument against 

the use of flight deck napping or in-flight sleep. It would not be desirable to have a 

crewmember who is woken up because of an emergency, but who is impaired by 

sleep inertia. This argument is based on the effects of sleep inertia seen in 

laboratory studies. However, studies of napping on the flight deck and of sleep in 

onboard crew rest facilities show that sleep in flight contains very little slow-wave 

sleep. (It is lighter and more fragmented than sleep on the ground). This means 

that sleep inertia is much less likely to occur waking up from sleep in flight than 

would be predicted from laboratory sleep studies. 
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The risk of sleep inertia can also be reduced by having a protocol for returning to 

active duty that allows time for sleep inertia to wear off. Overall, the demonstrated 

benefits of controlled napping and in-flight sleep greatly out-weigh the potential 

risks associated with sleep inertia. To reduce the risk of sleep inertia after flight 

deck napping, the recommendation is to limit the time available for the nap to 40 

minutes. Given the time taken to fall asleep, a 40-minute opportunity is too short 

for most people to enter slow-wave sleep. Refer to Appendix C for suggested 

Flight Operations Manual procedures for controlled napping. 

Rapid Eye Movement Sleep 

During Rapid Eye Movement sleep (REM sleep), brain activity measured by 

polysomnography looks similar to brain activity during waking. However in REM 

sleep, from time to time the eyes move around under the closed eyelids – the socalled ‘rapid eye movements’ –and this is often accompanied by muscle twitches 

and irregular heart rate and breathing. 

People woken from REM sleep can typically recall vivid dreaming. At the same 

time, the body cannot move in response to signals from the brain so dreams 

cannot be ‘acted out’. (The signals effectively get blocked in the brain stem and 

cannot get through to the spinal cord.) People sometimes experience brief 

paralysis when they wake up out of a dream, when reversal of this ‘REM block’ is 

slightly delayed. Because of these features, REM sleep is sometimes described as 

‘a highly activated brain in a paralyzed body’. 

Dreams have always been a source of fascination, but are difficult to study using 

quantitative scientific methods. They have been interpreted as everything from 

spiritual visitations to fulfillment of instinctual drives, to being a meaningless byproduct of activity in various parts of the brain during REM sleep. The current 

neuro-cognitive view of dreaming argues that it results from brief moments of 

consciousness when we become aware of all the processing that our brains 

normally do ‘off-line’, i.e. when they are not busy dealing with information coming in 

from the environment through the senses, and are not being directed by our 

conscious control. This ‘off-line’ processing includes reactivating memories and 

emotions from previous experiences, and integrating them with experiences from 

the latest period of waking. Dreams in this view are a glimpse into your brain 

reshaping itself so that you can wake up in the morning still yourself, but a slightly 

revised version as a result of your experiences yesterday, and ready to start 

interacting with the world again. 

People vary greatly in their ability to recall dreams, and we generally only recall 

them when we wake spontaneously out of REM sleep (and then only fleetingly 

unless we write them down or talk about them). Nevertheless, most adults normally 

spend about a quarter of their sleep time in REM sleep. 
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Non-REM/REM Cycles 

Across a normal night of sleep, non-REM sleep and REM sleep alternate in a cycle 

that lasts roughly 90 minutes (but is very variable in length, depending on a 

number of factors). Figure 2.1 is a diagram describing the non-REM/REM cycle 

across the night in a healthy young adult. Real sleep is not as tidy as this - it 

includes more arousals (transitions to lighter sleep) and brief awakenings. Sleep 

stages are indicated on the vertical axis and time is represented across horizontal 

axis3

. 

Figure 2.1: Diagram of the non-REM/REM cycle across the night in a young adult 

Sleep is entered through Stage 1 non-REM and then progresses deeper and 

deeper into non-REM. About 80-90 minutes into sleep, there is a shift out of slowwave sleep (non-REM stages 3 and 4). This is often marked by body movements, 

as the sleeper transitions briefly through Stage 2 non-REM and into the first REM 

period of the night. (REM periods are indicated as shaded boxes in Figure 2.1). 

After a fairly short period of REM, the sleeper progresses back down again through 

lighter non-REM sleep and into slow-wave sleep, and so the cycle repeats. 

The amount of slow-wave sleep in each non-REM/REM cycle decreases across 

the night, and there may be none at all in the later cycles. In contrast, the amount 

of REM sleep in each non-REM/REM cycle increases across the night. The 

sleeper depicted in Figure 2.1 wakes up directly out of the final REM period of the 

night, and so would probably recall dreaming. 

 

3

 Gander PH (2003) Sleep in the 24-Hour Society. Wellington, New Zealand: Open Mind Publishing. ISBN 0-909009-

59-7 
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Interestingly, slow-wave sleep always predominates at the beginning of a sleep 

period, regardless of when sleep occurs in the day/night cycle or in the circadian 

body clock cycle. There seems to be a priority to discharge the homeostatic sleep 

pressure first. In contrast, the time from sleep onset to the first bout of REM (the 

REM latency) and the duration of each REM bout varies markedly across the 

circadian body clock cycle. The circadian drive for REM sleep is strongest a few 

hours before normal wakeup time. These two processes – the homeostatic sleep 

process and the circadian body clock are the main components in most of the 

bio-mathematical models that are used to predict crewmember fatigue levels (see 

Chapter Four). 

Operational Note: 

Mitigation Strategies for Sleep Loss

Restoration of a normal non-REM/REM cycle is one measure of recovery from the 

effects of sleep loss. Lost sleep is not recovered hour-for-hour, although recovery 

sleep may be slightly longer than usual. 

• On the first recovery night, there is more slow-wave sleep than usual. Indeed, 

there can be so much slow-wave sleep that there is not enough time to make 

up REM sleep. 

• On the second recovery night, there is often more REM sleep than usual. 

• By the third recovery night, the non-REM/REM cycle is usually back to normal. 

Operationally, this means that schedules need to periodically include an 

opportunity for at least two consecutive nights of unrestricted sleep, to enable 

crewmembers to recover from the effects of sleep loss. 

This does not equate to 48 hours off. For example, 48 hours off duty starting at 

02:00 would only give most people the opportunity for one full night of unrestricted 

sleep. On the other hand, 40 hours off starting at 21:00 would give most people the 

opportunity for two full nights of unrestricted sleep. 

Additional nights may be needed for recovery if a crewmembers’ circadian body 

clock is not already adapted to the local time zone (see Section 2.3). 

2.2.2 The Issue of Sleep Quality 

Sleep quality (its restorative value) depends on going through unbroken nonREM/REM cycles (which suggests that both types of sleep are necessary and one 

is not more important than the other). The more the non-REM/REM cycle is 

fragmented by waking up, or by arousals that move the brain to a lighter stage of 

sleep without actually waking up, the less restorative value sleep has in terms of 

how you feel and function the next day. 

Operational Note: 

Mitigation Strategies to Minimize Sleep Interruptions

Because uninterrupted non-REM/REM cycles are the key to good quality sleep, 

operators should develop procedures that minimize interruptions to crewmembers’ 

sleep. 

Rest periods should include defined blocks of time (sleep opportunities) during 

which crewmembers are not contacted except in emergencies. These protected 

sleep opportunities need to be known to flight crews and all other relevant 

personnel. For example, calls from crew scheduling should not occur during a rest 

period as they can be extremely disruptive. 
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Operators should also develop procedures to protect crewmember sleep at layover 

and napping facilities. For example, if a rest period occurs during the day at a 

layover hotel, the operator could make arrangements with the hotel to restrict 

access to the section of the hotel where crewmembers are trying to sleep (such as 

no children, crewmembers only) and instruct their staff to honor the necessary 

quiet periods (for example, no maintenance work or routine cleaning 

Quality of In-Flight Sleep 

As mentioned above, polysomnography studies show that crewmembers’ sleep in 

onboard crew rest facilities is lighter and more fragmented than sleep on the 

ground4

. Sleep during flight deck naps is also lighter and more fragmented than 

would be predicted from laboratory studies5

. Nevertheless, there is good evidence 

that in-flight sleep improves subsequent alertness and reaction speed and is a 

valuable mitigation strategy in an FRMS. 

Interestingly, studies of sleep in hypobaric chambers at pressures equivalent to 

cabin pressure at cruising altitude indicate that the fragmented quality of in-flight 

sleep is not due to altitude6

. Several studies have asked crewmembers what 

disturbs their sleep on board. The factors most commonly identified are random 

noise, thoughts, not feeling tired, turbulence, ambient aircraft noise, inadequate 

bedding, low humidity, and going to the toilet.. 

Sleep Quality and Aging 

Across adulthood, the proportion of sleep time spent in slow-wave sleep declines, 

particularly among men. In addition, sleep becomes more fragmented. For 

example, one study with 2,685 participants aged 37–92 yrs found that the average 

number of arousals (transitions to lighter sleep and awakenings) rose from 16 per 

hour of sleep for 30-54 year-olds to 20 per hour of sleep for 61-70 year-olds7

. 

These age-related trends are seen in the sleep of flight crewmembers, both on the 

ground and in the air2,8

. A study of in-flight sleep on delivery flights of B-777 aircraft 

(from Seattle to Singapore or Kuala Lumpur) found that age was the factor that 

most consistently predicted the quality and duration of bunk sleep. Older pilots took 

longer to fall asleep, obtained less sleep overall, and had more fragmented sleep. 

It is not yet clear whether these age-related changes in sleep reduce its 

effectiveness for restoring waking function. Laboratory studies that experimentally 

fragment sleep are typically conducted with young adults. On the flight deck, 

experience (both in terms of flying skills and knowing how to manage sleep on 

trips) could help reduce potential fatigue risk associated with age-related changes 

in sleep. 

 

4

 Signal, T.L., Gale, J., and Gander, P.H. (2005) Sleep Measurement in Flight Crew: Comparing Actigraphic and 

Subjective Estimates of Sleep with Polysomnography. Aviation Space and Environmental Medicine 76(11):1058-

1063 5

 Rosekind, M.R., Graeber, R.C., Dinges, D.F., et al., (1994) Crew Factors in Flight Operations IX: Effects of planned 

cockpit rest on crew performance and alertness in long haul operations. NASA Technical Memorandum 108839, 

Moffett Field: NASA Ames Research Center. 

6

 Mumm, J.M., Signal, T.L., Rock, P.B., Jones, S.P., O’Keeffe, K.M., Weaver, M. R., Zhu, S., Gander, P.H., Belenky, 

G. (2009) Sleep at simulated 2438 m: effects on oxygenation, sleep quality, and post-sleep performance. Aviation, 

Space, and Environmental Medicine 80 (8):691-697. 7

 Redline, S., Kirchner, H.L., Quan, S.F., Gottlieb, D.J., Kapur, V., Newman, A. (2004). The effects of age, sex, 

ethnicity, and sleep-disordered breathing on sleep architecture. Archives of Internal Medicine 164:406–418. 8

 Signal, T.L., Gander, P.H., van den Berg, M. (2004) Sleep in flight during long rest opportunities. Internal Medicine 

Journal 34(3): A38. 
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Sleep Disorders 

The quality of sleep can also be disrupted by a wide variety of sleep disorders, 

which make it impossible to obtain restorative sleep, even when people spend 

enough time trying to sleep. Sleep disorders pose a particular risk for flight 

crewmembers because, in addition, they often have restricted time available for 

sleep. It is recommended that FRMS training (Chapter Six) should include basic 

information on sleep disorders and their treatment, where to seek help if needed, 

and any requirements relating to fitness to fly. 

2.2.3 Consequences of Not Getting Enough Sleep 

Even for people who have good quality sleep, the amount of sleep they obtain is 

very important for restoring their waking function. An increasing number of 

laboratory studies are looking at the effects of ‘trimming’ sleep at night by an hour 

or two (known as sleep restriction). There are several key findings from these 

studies that are important for FRMS. 

1. The effects of restricting sleep night after night accumulate, so that people 

become progressively less alert and less functional day after day. This is 

sometimes described as accumulating a sleep debt. This is a common 

occurrence for crewmembers (see below), for example when minimum rest 

periods are scheduled for several days in a row. 

2. The shorter the time allowed for sleep each night, the faster alertness and 

performance decline. For example, one laboratory study found that spending 7 

hours in bed for 7 consecutive nights was not enough to prevent a progressive 

slowing down in reaction time9

. The decline was more rapid for a group of 

participants who spent only 5 hours in bed each night, and even more rapid for 

a group who spent only 3 hours in bed each night. This is described as a 

dose-dependent effect of sleep restriction. 

3. The pressure for sleep increases progressively across successive days of 

sleep restriction. Eventually, it becomes overwhelming and people begin falling 

asleep uncontrollably for brief periods, known as micro-sleeps. During a 

micro-sleep, the brain disengages from the environment (it stops processing 

visual information and sounds). In the laboratory, this can result in missing a 

stimulus in a performance test. Driving a motor vehicle, it can result in failing to 

take a corner. Similar events have been recorded on the flight deck during 

descent into major airports5

. 

4. Full recovery of waking function after sleep restriction can take longer than 

two nights of recovery sleep (i.e., longer than it takes the non-REM/REM 

cycle to recover). Indeed, chronic sleep restriction may have effects on the 

brain that can affect alertness and performance days to weeks later10. 

5. For the first few days of severe sleep restriction (for example, 3 hours in bed), 

people are aware that they are getting progressively sleepier. However, after 

several days they no longer notice any difference in themselves, even 

although their alertness and performance continues to decline. In other words, 

as sleep restriction continues, people become increasingly unreliable at 

assessing their own functional status. This finding raises a question about the 

reliability of subjective ratings of fatigue and sleepiness as measures of a 

crewmember’s level of fatigue-related impairment (see Appendix B). 

 

9

 Belenky, G., Wesensten, N.J., Thorne, D.R., et al. (2003). Patterns of performance degradation and restoration 

during sleep restriction and subsequent recovery: a sleep dose-response study. Journal of Sleep Research 12:1-12. 10 Rupp, T.L., Wesensten, N.J, Bliese, P.D. et al. (2009). Banking sleep: realization of benefits during subsequent 

sleep restriction and recovery. Sleep 32 (3): 311-321 
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6. At least in the laboratory, some people are more resilient to the effects of sleep 

restriction than others. Currently, there is a lot of research effort aimed at trying 

to understand why this is, but it is still too early for this to be applied in an 

FRMS (for example, by recommending different personal mitigation strategies 

for people who are more or less affected by sleep restriction). 

In general, more complex mental tasks such as decision making and 

communication seem to be more severely affected by sleep loss than simpler 

tasks. Brain imaging studies also suggest that the brain regions involved in more 

complex mental tasks are the most affected by sleep deprivation and have the 

greatest need for sleep to recover their normal function. 

Laboratory sleep restriction studies are currently the main source of information on 

the effects of sleep restriction. However, they have some obvious limitations. The 

consequences of reduced alertness and poor task performance are quite different 

in the laboratory than for crewmembers on duty. Laboratory studies usually look at 

the effects of restricting sleep at night and participants sleep in a dark, quiet 

bedroom. This may mean that current understanding is based on a ‘best case 

scenario’. More research is needed on the effects of restricting sleep during the 

day, and on the combination of restricted sleep and poor quality sleep. Laboratory 

studies also focus on the performance of individuals, not people working together 

as a crew. 

One simulation study with 67 experienced B747-400 crews has demonstrated that 

sleep loss increased the total number of errors made by the crew11. The study 

design was set up so that the pilot in command was always the pilot flying. 

Paradoxically, greater sleep loss among first officers improved the rate of error 

detection. On the other hand, greater sleep loss among pilots in command led to a 

higher likelihood of failure to resolve errors that had been detected. Greater sleep 

loss was also associated with changes in decision making, including a tendency to 

choose lower risk options, which would help mitigate the potential fatigue risk. 

Simulator studies like this are expensive and logistically complex to conduct 

properly, but they provide vital insights on the links between crewmember sleep 

and operational fatigue risk. 

Sleep Restriction in Flight Operations 

The idea of sleep restriction implies that there is an optimum amount of sleep that 

people need to obtain each night. The concept of individual sleep need is an area 

of active debate in sleep research. One way to measure sleep restriction that 

avoids this problem is to look at how much sleep crewmembers obtain when they 

are at home between trips, compared to how much sleep they obtain during trips. 

Table 2.1 summarizes data on sleep restriction across different flight operations 

that were monitored by the NASA Fatigue Program in the 1980s12. In these 

studies, crewmembers completed sleep and duty diaries before, during, and after a 

scheduled commercial trip. For each crewmember, his average sleep duration per 

24 hours at home before the trip was compared with his average sleep duration 

per 24 hours on the study trip. During night cargo and long haul trips, 

crewmembers often had split sleep (slept more than once in 24 hours). 

 

11 Thomas, M.J.W., Petrilli, R.M., Lamond, N.A., et al. (2006). Australian Long Haul Fatigue Study. In: Enhancing 

Safety Worldwide: Proceedings of the 59th Annual International Air Safety Seminar. Alexandria, USA, Flight Safety 

Foundation. 12 Gander, P.H., Rosekind, M.R., and Gregory, K.B. (1998) Flight crew fatigue VI: an integrated overview. Aviation, 

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Scheduling has undoubtedly changed since these studies, so the data in Table 2.1 

are likely to be unrepresentative of the current situation in many cases. However, 

they indicate that sleep restriction is very common across different types of flight 

operations. 

Table 2.1: Sleep restriction during commercial flight operations 

Short Haul Night Cargo Long Haul 

Crewmembers averaging at least 1 

hour of sleep restriction per trip day 67% 54% 43% 

Crewmembers averaging at least 2 

hours of sleep restriction per trip day 30% 29% 21% 

Length of trip 3-4 days 8 days 4-9 days 

Time zones crossed per day 0-1 0-1 0-8 

Number of crewmembers studied 44 34 28 

Note: The night cargo trips included a 1-2 night break in the sequence of night 

shifts. 

 Splitting long haul trips into 24 hours days is rather arbitrary, because the 

average duty day lasted 10.2 hours and the average layover lasted 24.3 

hours. 

A growing amount of evidence, from both laboratory studies and from 

epidemiological studies that track the sleep and health of large numbers of people 

across time, indicates that chronic short sleep may have negative effects on health 

in the long term. This research suggests that short sleepers are at greater risk of 

becoming obese and developing type-2 diabetes and cardiovascular disease. 

There is still debate about whether habitual short sleep actually contributes to 

these health problems, or is just associated with them. In addition, flight 

crewmembers as a group are exceptionally healthy compared to the general 

population. What is clear is that good health depends not only on good diet and 

regular exercise, but also on getting enough sleep on a regular basis. Sleep is 

definitely not a tradable commodity. 

Operational Note: 

Mitigation Strategies for Managing Sleep Debt

Sleep restriction is common across different types of flight operations. Because the 

effects of sleep restriction are cumulative, schedules must be designed to allow 

periodic opportunities for recovery. Recovery opportunities need to occur more 

frequently when daily sleep restriction is greater, because of the more rapid 

accumulation of fatigue. 

The usual recommendation for a recovery opportunity is for a minimum of two 

consecutive nights of unrestricted sleep. Some recent laboratory studies of sleep 

restriction suggest that this may not be enough to bring crewmembers back up to 

their optimal level of functioning. There is evidence that the sleep-restricted brain 

can stabilize at a lower level of functioning for long periods of time (days to weeks). 
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Especially in irregular operations, procedures that allow a crewmember to continue 

sleeping until needed can reduce the rate of accumulation of sleep debt. For 

example, if an aircraft with an anticipated repair time of 0730 will not actually be 

ready until 11:30, then a reliable procedure that allows the crew member to 

continue sleeping would be beneficial. One airline has a system where the 

operator contacts the layover hotel to update the report time by slipping a message 

under the crewmember’s door. The hotel provides a wakeup call one hour before 

pick up time. 

2.3 INTRODUCTION TO CIRCADIAN RHYTHMS

Sleeping at night is not just a social convention. It is programmed into the brain by the 

circadian body clock, which is an ancient adaptation to life on our 24-hour rotating planet. 

Even very ancient types of living organisms have something equivalent, which means that 

circadian biological clocks have been around for several billion years. 

A feature of circadian clocks is that they are light sensitive. The human circadian clock 

monitors light intensity through a special network of cells in the retina of the eye (this special 

light input pathway to the circadian clock is not involved in vision). The clock itself resides in 

a fairly small cluster of cells (neurons) deeper in the brain (in the suprachiasmatic nuclei 

(SCN) of the hypothalamus). The cells that make up the clock are intrinsically rhythmic, 

generating electrical signals faster during the day than during the night. However, they have 

a tendency to produce an overall cycle that is a bit slow – for most people the ‘biological day’ 

generated by the circadian body clock is slightly longer than 24 hours. The sensitivity of the 

circadian body clock to light enables it to stay in step with the day/night cycle. However, that 

same sensitivity to light also creates problems for crewmembers who have to sleep out of 

step with the day/night cycle (for example on domestic night cargo operations), or who have 

to fly across time zones and experience sudden shifts in the day/night cycle. 

2.3.1 Examples of Circadian Rhythm 

It is not possible to directly measure the electrical activity of the circadian body 

clock in human beings. However, almost every aspect of human functioning 

(physical or mental) undergoes daily cycles that are influenced by the circadian 

body clock. Measuring overt rhythms in physiology and behaviour is like watching 

the hands of an (analogue) wrist watch. The hands move around the watch face 

because they are driven by the time-keeping mechanism inside the watch, but they 

are not part of the time-keeping mechanism itself. Similarly, most circadian 

rhythms that can be measured, such as rhythms in core body temperature or selfrated fatigue, are driven by the circadian body clock, but they are not part of the 

biological time-keeping mechanism. 

Figure 2.2 shows an example of circadian rhythms in core body temperature and 

self-rated fatigue of a 46-year old short haul crewmember monitored before, 

during, and after a 3-day pattern of flying on the east coast of the USA (staying in 

the same time zone)13. The crewmember had his core temperature monitored 

continuously and kept a sleep and duty diary, in which he noted his sleep times 

and rated the quality of his sleep, as well as rating his fatigue every 2 hours while 

he was awake (on a scale from 0 = most alert to 100 = most drowsy). 

 

13 Gander, P.H., Graeber , R.C., Foushee, H.C., Lauber, J.K., Connell, L.J. (1994). Crew Factors in Flight Operations 

II: Psychophysiological Responses to Short-Haul Air Transport Operations. NASA Technical Memorandum #108856. 

Moffett Field: NASA Ames Research Center. 
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Core body temperature typically fluctuates by about 1 ̊C across the 24-hour day. 

Note that the crewmember's core temperature starts to rise each morning before 

he wakes up. In effect, his body is beginning to prepare ahead of time for the 

greater energy demands of being more physically active. (If body temperature only 

began to rise after he started to be more physically active, it would be a lot harder 

to get up in the morning). 

Looking at his self-rated fatigue, this crewmember did not feel at his best first thing 

in the morning. He tended to feel least fatigued about 2-4 hours after he woke up, 

after which his fatigue climbed steadily across the day. The dashed line across the 

sleep period indicates that he was not asked to wake up every 2 hours to rate his 

fatigue across this time. 

Figure 2.2: Circadian rhythms of a short haul pilot 

Core body temperature is often use as a marker rhythm to track the cycle of the 

circadian body clock because it is relatively stable and easy to monitor. However, 

no measurable rhythm is a perfect marker of the circadian body clock cycle. For 

example, changes in the level of physical activity also cause changes in core 

temperature, which explains the small peaks and dips in temperature in Figure 2.2. 

The daily minimum in core body temperature corresponds to the time in the 

circadian body clock cycle when people generally feel most sleepy and are least 

able to perform mental and physical tasks. This is sometimes described as the 

Window of Circadian Low (WOCL). 
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2.3.2 The Circadian Body Clock and Sleep 

As mentioned in Section 2.2, the circadian body clock influences sleep in a number 

of ways. (It has connections to centers in the brain that promote wakefulness and 

to opposing centers that promote sleep, as well as to the system that controls REM 

sleep.) Figure 2.3 is a diagram that summarizes the effects of the circadian clock 

on sleep. It is based on data collected from 18 night cargo pilots on their days off, 

i.e., when they were sleeping at night14. Like the crewmember in Figure 2.2, they 

also had their core temperature monitored continuously, and kept sleep and duty 

diaries. 

The core temperature rhythm is summarized as a simple (continuous) curve. The 

daily time of the minimum in temperature (shown by the black dot) is the average 

for all crewmembers and is used as a reference point for describing the other 

rhythms. Note that changes in temperature are not the cause of the other rhythms. 

The core body temperature rhythm is being ‘read’ like the hands of an analogue 

wrist watch, as a way of following the underlying cycle of the circadian body clock. 

Figure 2.3: Summary of the influences of the circadian body clock on sleep at night 

 

14 Gander, P.H., Rosekind, M.R., and Gregory, K.B. (1998) Flight crew fatigue VI: an integrated overview. Aviation, 

Space, and Environmental Medicine 69: B49-B60 
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Figure 2.3 summarizes the following features of sleep at night (when 

crewmembers are fully adapted to the local time zone). 

• Sleep normally begins about 5 hours before the minimum in core body 

temperature. 

• Wakeup normally occurs about 3 hours after the minimum in core body 

temperature. 

• REM sleep is entered fastest, and REM periods are longest and most intense, 

just after the minimum in core body temperature. This is sometimes described 

as the peak of the circadian rhythm in REM propensity (the dashed curve in 

Figure 2.3). 

• A variety of laboratory protocols have demonstrated people are extremely 

unlikely to fall asleep 6-8 hours before the minimum in core body temperature. 

This has become known as the evening wake maintenance zone. 

• Laboratory studies also show that as body temperature begins to rise, there is 

an increasing pressure to wake up. This peaks about 6 hours after the 

circadian temperature minimum. This is sometimes referred to as an internal 

alarm clock, because it is very hard to fall asleep or stay asleep during this 

part of the circadian body clock cycle. 

The interaction between the homeostatic pressure for sleep and the circadian 

variation in sleepiness driven by the body clock results in two times of peak 

sleepiness in 24 hours; 

• A peak in the early hours of the morning – the so-called Window of Circadian 

Low (WOCL), which occurs around 3-5 am for most people; and 

• A peak in the early afternoon - sometimes called the afternoon nap window 

(around 3-5 pm for most people). Restricted sleep at night, or disturbed sleep 

makes it harder to stay awake during the next afternoon nap window. 

The precise timing of the two peaks in sleepiness is different in people who are 

morning types (whose circadian rhythms and preferred sleep times are earlier 

than average) and evening types (whose circadian rhythms and preferred sleep 

times are later than average). Across the teenage years, most people become 

more evening-type. Across adulthood, most people become more morning-type. 

This progressive change towards becoming more morning-type has been 

documented in flight crewmembers across the age range 20-60 years. 

The combined effects of the homoeostatic pressure for sleep and the circadian 

biological clock can be thought of as defining ‘windows’ when sleep is promoted 

(the early morning and afternoon times of peak sleepiness) and ‘windows’ when 

sleep is opposed (the time of the internal alarm clock in the late morning, and the 

evening wake maintenance zone). 

Operational Note: 

The Circadian Body Clock, Sleep, and FRMS

• The daily minimum in core body temperature corresponds to the time in the 

circadian body clock cycle when people feel most sleepy and are least able to 

perform mental and physical tasks. This is sometimes called the Window of 

Circadian Low (WOCL) and it is a time of high risk for fatigue-related error. 

In FRMS incident investigations, it is important to estimate the time that errors 

occur relative to the expected time of the WOCL. The WOCL can occur in 

flight during domestic night operations and during long haul and ULR 

operations when the duty/rest cycle is out of step with crewmembers’ 

circadian body clock cycles. 
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• The evening wake maintenance zone occurs in the few hours before usual 

bedtime. This makes it very difficult to fall asleep early the night before an 

early duty report time. This has been identified a cause of restricted sleep and 

increased fatigue risk in short haul operations that require early starts. 

• The increasing drive for wake that accompanies the increase in core body 

temperature in the morning makes it difficult to fall asleep or stay asleep later 

in the morning and in the early afternoon. This has been identified as a cause 

of restricted sleep and increased fatigue risk in night cargo operations, which 

require crewmembers to delay their main sleep period until the morning. 

• The internal alarm clock and the evening wake maintenance zone can also 

interfere with the in-flight sleep and layover sleep of long haul and ULR 

crewmembers when the duty/rest cycle is out of step with crewmembers’ 

circadian body clock cycles. 

2.3.3 Sensitivity of the Circadian Body Clock to Light 

At the beginning of this Chapter, there was a brief description of how the circadian 

body clock is able to track light intensity in the environment. This enables it to stay 

in step with the day/night cycle, even although it has a tendency to generate a 

‘biological day’ that is slightly longer than 24 hours. 

The effect of light on the circadian body clock changes according to when in the 

clock cycle the light exposure occurs. For a crewmember adapted to local time and 

sleeping at night: 

• light exposure in the morning (after the temperature minimum) causes the 

circadian clock to speed up temporarily, resulting in a phase advance 

(equivalent to crossing time zones in an eastward direction); 

• light exposure in the middle of the day has very little effect; and 

• light exposure in the evening (before the temperature minimum) causes the 

circadian clock to slow down temporarily, resulting in a phase delay 

(equivalent to crossing time zones in a westward direction). 

Bright light causes bigger shifts in the circadian body clock cycle than dim light, 

and the clock is particularly sensitive to blue light. 

In theory, this means that just the right amount of light exposure at the same time 

every morning would speed up a 24.5-hour circadian clock cycle just enough to 

synchronize it to exactly 24 hours. In practise, staying in step with the day/night 

cycle is more complex than this. In modern industrialised societies, people have 

very haphazard exposures to light, particularly bright outdoor light. In addition, the 

circadian body clock is sensitive to other time cues from the environment, notably 

social cues, and can also be moved backwards or forwards in its cycle by bouts of 

physical activity. 

The ability of the circadian clock to ’lock on’ to the 24-hour day/night cycle is a key 

feature of its usefulness for most species, enabling them to be diurnal or nocturnal 

as needed to enhance their survival. However, it has become a disadvantage in 

the 24/7 society because it causes the human circadian body clock to resist 

adaptation to any pattern other than sleep at night. 
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2.3.4 Shift Work 

From the perspective of human physiology, shift work can be defined as any duty 

pattern that requires a crewmember to be awake during the time in the circadian 

body clock cycle that they would normally be asleep. 

The further sleep is displaced from the optimum part of the circadian body clock 

cycle, the more difficult it becomes for crewmembers to get adequate sleep (i.e., 

the more likely they are to experience sleep restriction). For example, 

crewmembers flying domestic night cargo operations are typically on duty through 

most of the optimum time for sleep in the circadian body clock cycle. This happens 

because the circadian body clock is ‘locked on’ to the day/night cycle, and does not 

flip its orientation to promote sleep during the day when crewmembers are flying at 

night. 

Figure 2.4 summarises what happened to the circadian biological clock and sleep 

when the night cargo crewmembers in Figure 2.3 were flying at night and trying to 

sleep in the morning. (Recall that they had their core temperature monitored 

continuously across 8 day-trip patterns, and kept sleep and duty dairies.) 

The core temperature rhythm is summarized as a simple (continuous) curve. 

Looking back at Figure 2.3, when these crewmembers were off duty and sleeping 

at night, the average time of the temperature minimum was 05:20. In Figure 2.4, 

when they were working through the night, the average time of the temperature 

minimum shifted to 08:08 (a delay of 2 hours 48 minutes). This confirms that the 

circadian body clock did not adapt fully to night duty (which would have required a 

shift of about 12 hours). 

Figure 2.4: The circadian body clock and sleep after night duty 
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The incomplete adaptation of the circadian clock forced crewmembers to sleep in a 

different part of the circadian body clock cycle after night duty. 

• At home before the trip (Figure 2.3), they went to sleep about 5 hours before 

the temperature minimum and woke up about 3 hours after the temperature 

minimum. 

• After night duty (Figure 2.4), they went to sleep close to the circadian 

temperature minimum and woke up about 6 hours later. The average time of 

waking up after morning sleep periods was 14:13. The predicted time of the 

internal alarm clock (6 hours after the temperature minimum) was 14:08. 

Crewmembers were not asked what woke them up, but they rated themselves 

as not feeling well-rested after these restricted morning sleep episodes. 

Another consequence of the incomplete adaptation of the circadian body clock to 

night duty was that crewmembers were often operating the last flight of the night in 

the Window of Circadian Low (WOCL) when they would be expected to be sleepy 

and having to make additional effort to maintain their performance. No fatiguerelated incidents were observed on these flights (all crews were accompanied by a 

flight deck observer). However, all flights were routine, i.e., there were no 

operational events that tested the capacity of these crewmembers to respond to 

non-routine situations. 

Operational Note: 

Mitigation Strategies for Night Duty

• Night duty forces crewmembers to sleep later than normal in their circadian 

body clock cycle. This means that they have a limited amount of time to sleep 

before the circadian body clock wakes them up. Consequently, they need to 

get to sleep as soon as possible after coming off duty. 

• Getting off duty earlier increases the time available for sleep in the morning, 

before the circadian body clock makes it difficult for crewmembers to stay 

asleep. 

• Napping before going on duty is beneficial to help maintain alertness and 

performance through to the end of the night 

• Napping during the duty period (for example, on the ground while aircraft are 

being loaded and unloaded) is beneficial to help maintain alertness and 

performance through to the end of the night. The napping opportunity should 

be limited to 40-45 minutes, with an additional 10-15 minutes allowed to 

ensure that sleep inertia (if any) has dissipated. 

• In some operations, it may be possible to schedule a longer sleep opportunity 

during the night, for example during loading and unloading of freight, or during 

continuous duty overnight periods. Providing a sleeping room away from the 

aircraft and protected time to sleep would increase the amount of sleep that 

crewmembers are able to obtain. Once again 10-15 minutes allowed, to 

ensure that sleep inertia (if any) has dissipated. 
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2.3.5 Jet Lag 

Flying across time zones exposes the circadian body clock to sudden shifts in the 

day/night cycle. Because of its sensitivity to light and (to a lesser extent) social 

time cues, the circadian body clock will eventually adapt to a new time zone. 

Studies with participants flown as passengers have identified a number of factors 

that affect the rate of adaptation to a new time zone. These factors include the 

following. 

1. The number of time zones crossed - adaptation generally takes longer when 

more time zones are crossed. 

2. The direction of travel - adaptation is usually faster after westward travel than 

after eastward travel across the same number of time zones. 

a) This probably reflects the fact that most people have a circadian body 

clock that has an innate cycle slightly longer than 24 hours, which makes 

it easier to lengthen the cycle to adapt to a westward shift (a phase 

delay). 

b) After eastward flights across 6 or more time zones, the circadian body 

clock may adapt by shifting in the opposite direction, for example shifting 

18 time zones west rather than 6 time zones east. When this happens 

some rhythms shift eastward and others westward (known as 

resynchronization by partition) and adaptation can be particularly slow. 

3. Rhythms in different functions can adapt at different rates, depending on how 

strongly they are influenced by the circadian body clock. 

a) This means that during adaptation to the new time zone, rhythms in 

different body functions can be disturbed from their usual relationships to 

one another. 

4. Adaptation is faster when the circadian body clock is more exposed to the time 

cues that it needs to lock onto in the new time zone. This relates to the extent 

to which people adopt the pattern of sleep, eating etc, in the new time zone 

and the amount of time they spend outdoors in the first few days. 

5. Beginning a trip with a sleep debt seems to increase the duration and severity 

of jet lag symptoms. 

During the period of adaptation to the new time zone, common symptoms include 

wanting to eat and sleep at times that are out of step with the local routine, 

problems with digestion, degraded performance on mental and physical tasks, and 

mood changes. 

The situation for long haul and ultra-long range flight crew is different to that for the 

passenger who plans to spend long enough at the destination to adapt fully to local 

time. Typically, layovers in each destination last only 1-2 days, after which 

crewmembers are asked to operate a return flight or additional flights in the 

destination region, followed by the return flight(s) to their city of origin. This means 

that the circadian body clock does not have enough time to adapt to any of the 

destination time zones. In addition, the combination of a long duty day followed by 

1-2 day layovers gives a duty/rest cycle that does not follow a regular 24-hour 

pattern, so the circadian body clock cannot lock on to the duty/rest cycle. 
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Relatively few studies have tracked the circadian body clock across commercial 

long-haul trip patterns and none have tracked it across ULR operations. Figure 2.5 

depicts data from one NASA study conducted in the mid-1980s on B747 200/300 

operations (3-person crews consisting of a pilot in command, first officer, and flight 

engineer) 15. Similar trip patterns are still being flown by some operators but with an 

additional pilot, not a flight engineer. Participants had their core body temperature 

monitored continuously and kept sleep and duty diaries before, during, and after 

this trip, which included 4 trans-Pacific flights plus one round trip within Asia (NRTSIN-NRT). The dots on the graph indicate the time of the temperature minimum 

(averaged for 6 crewmembers per day). 

Figure 2.5: Study tracking the circadian body clock across multiple trans-Pacific 

flights 

By the end of this trip pattern, the temperature minimum had delayed by about 4.5 

hours, giving an average drift rate of about 30 minutes per 24 hours (or an average 

cycle length of the circadian body clock of about 24.5 hours). The drift presumably 

was the result of the fact that the circadian body clock did not have any 24-hour 

time cues to lock on to, with the non-24 hr duty/rest cycle and every layover in a 

different time zone. 
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One consequence was that the temperature minimum (corresponding to the 

Window of Circadian Low or WOCL) sometimes occurred in flight, for example 

on the last flight from NRT to SFO. At these times, crewmembers would be 

expected to be sleepy and having to make additional effort to maintain their 

performance. This would be an ideal time to take an in-flight nap (crewmembers 

did not have in-flight sleep opportunities on this trip). 

Another consequence was that when crewmembers returned home, their circadian 

body clocks were on average 4.5 hours delayed with respect to local time and took 

several days to readapt. 

Layover Sleep Patterns on Long-Haul and ULR Trips 

The fact that long haul and ULR crewmembers seldom stay long enough in any 

destination time zone to become adapted to local time has effects on their layover 

sleep. Often, crewmembers split their sleep, having one sleep period on local night 

and another corresponding to local night in their home time zone, which overlaps 

the preferred part of the circadian body clock cycle for sleep (at least for the first 

24-48 hours in a new time zone). 

Another factor affecting layover sleep, particularly for un-augmented crews who do 

not have the opportunity for in-flight sleep, is that long haul duty days are often 

associated with extended periods of waking. For example, in a series of long haul 

trips studied by the NASA Fatigue Program the average period of waking 

associated with a duty day was 20.6 hours (the average length of a duty period 

was 9.8 hours)13. Across these long periods of waking, the homeostatic 

pressure for sleep builds so that crewmembers tend to sleep, at least for a short 

time, soon after arrival at the destination layover hotel. For example, this is a 

common pattern after eastward night flights across multiple time zones. A short 

sleep is taken soon after arrival, during the local afternoon, and then the main 

sleep period is then taken during local night. 

FRMS training for long haul and ULR crewmembers needs to include discussion of 

the effects of trans-meridian flights on the circadian body clock and sleep. One way 

to reduce the complexity of this material is to develop specific guidance for sleep 

and the use of personal fatigue mitigation strategies on different routes. 

Operational Note: 

Effects of Different Types of Long Haul Trip Patterns on the Circadian Body Clock

Relatively few studies have tracked the circadian body clock across long haul trip 

patterns, and many are over 20 years old. The available studies suggest that 

different types of trip patterns affect the circadian body clock in different ways. 

• Sequences of back-to-back trans-meridian flights (separated by 24 hour 

layovers) that do not return to the domicile time zone for long periods of time 

(such as the pattern illustrated in Figure 2.5) tend to cause the circadian body 

clock to drift on its innate cycle, which is typically slightly longer than 24 hours. 

This is probably because these trips contain no regular 24-hour pattern to 

which the circadian body clock can synchronize. When they arrive back in 

their home time zone, crewmembers need additional days to readapt to local 

time. 
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• Sequences of out-and-back transmeridan flights (separated by 24 hour 

layovers) that return to the home time zone on alternate layovers seem to 

enable the circadian body clock to remain synchronized to the home time 

zone. For example, a trip pattern studied by the NASA Fatigue Program 

involved three back-to-back return flights between the US West Coast and 

London (6 flights in total) with 24-hour layovers between each flight. Returning 

to their home time zone on every second layover appeared to keep 

crewmembers’ circadian body clocks (monitored by the core temperature 

rhythm) synchronized to West Coast time. As a result, crewmembers obtained 

relatively good sleep on the West Coast layovers and did not need additional 

days to readapt to West Coast time at the end of the trip. 

• There is some evidence that when crewmembers stay longer in the 

destination region, for example doing several days of local flying with minimal 

time zone changes before flying the long haul trip home, their circadian body 

clocks begin to adapt to the destination time zone. This may improve layover 

sleep. On the other hand, when they arrive back in their home time zone, they 

need additional days to readapt to local time. 

The scarcity of data on what happens to the circadian body clock across different 

long haul trip patterns is one reason most current bio-mathematical models do not 

have a validated approach for simulating what happens to the circadian clock 

across sequences of trans-meridian flights (see Chapter Four). 

2.4 SUMMARY OF ESSENTIAL SCIENCE FOR FRMS 

Discoveries in sleep science and circadian rhythms provide a strong scientific basis for 

FRMS. The science does not address every detailed operational question and it never will. In 

other words, there will always be a need to combine operational experience and scientific 

knowledge to come up with workable controls and mitigations to manage fatigue risk in an 

FRMS. 

The scientific basis for FRMS can be continuously improved if data that are routinely 

collected as part of FRM processes (Chapter Four) and FRMS Assurance processes 

(Chapter Five) can be shared in appropriate ways in the public domain. 

Operational Note: 

Key Facts about Sleep

Sleep is vital for recovery from fatigue. Two aspects of sleep are important – the amount of 

sleep and the quality of sleep. 

Amount of Sleep

• Sleep restriction is common in flight operations. 

• Not getting enough sleep leads to: feeling sleepier, difficulty staying alert, getting 

irritable, slower reactions, poorer coordination, slower thinking, getting fixated on part of 

a problem and losing the big picture (loss of situation awareness), less creative problem 

solving, and reduced memory consolidation (impaired learning). 

• The effects of restricted sleep accumulate: 

− the rate of accumulation of fatigue is related to the rate of sleep loss (less sleep 

per day = more rapid accumulation of fatigue); 

− sleep pressure eventually becomes uncontrollable, which results in unintentional 

sleep (micro sleeps or unintended naps). 
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• Lost hours of sleep do not need to be recovered hour-for-hour. 

• At least two consecutive nights of unrestricted sleep are required to recover from the 

cumulative effects of multiple nights of restricted sleep. Unrestricted sleep means being 

free to fall asleep when tired and wake up spontaneously, with sleep occurring at the 

appropriate time in the cycle of the circadian body clock. In some cases, this recovery 

period can be built into schedules (for example with short day time duty periods). 

• Controlled napping can temporarily relieve the symptoms of sleep loss. It is a valuable 

personal mitigation strategy, for example prior to a night duty period or on long haul 

flights. 

− A NASA study of flight deck napping showed improved alertness at the end of 

unaugmented long haul flights (8-9 hrs) when flight crew members were given a 

40-min nap opportunity in their flight deck seat 

Quality of Sleep

• Good quality sleep involves regular cycles through two different types of sleep – Rapid 

Eye Movement sleep (REM sleep) and non-REM sleep. A full non-REM/REM sleep 

cycle takes roughly 90 minutes. 

• Sleep that is fragmented by multiple awakenings, or arousals into lighter stages of 

sleep, breaks up the non-REM/REM cycle and is less restorative than continuous sleep. 

− Sleep in onboard crew rest facilities is lighter and more fragmented than sleep in 

hotels or at home. This does not appear to be an effect of altitude. 

• Both flight deck naps and in-flight sleep in crew rest facilities contain very little deep 

non-REM sleep (known as slow-wave sleep), so sleep inertia is less likely after in-flight 

sleep than is predicted by laboratory studies. 

Two main physiological processes interact to regulate sleep

1. The homeostatic sleep process is evident in the pressure for slow-wave sleep that 

builds up across waking and discharges across sleep. 

2. The circadian body clock regulates the timing of REM sleep and dictates the preference 

for sleep at night. 

The interaction between the homeostatic pressure for sleep and the circadian body clock 

results in two times of peak sleepiness in 24 hours: 

• A peak in the early afternoon (the afternoon nap window) that occurs around 3-5 pm for 

most people; and 

• A peak in the early hours of the morning (the window of circadian low or WOCL) that 

occurs around 3-5 am for most people. 

Note: These two processes are the main components in most of the bio-mathematical 

models that are used to predict crewmember fatigue levels (see Chapter Four) 

Operational Note: 

Key Facts about the Circadian Body Clock

• The circadian body clock is a pacemaker in the brain that is sensitive to light through a 

specialized input pathway from the eyes (separate from vision). 

• The circadian biological clock generates an innate ‘biological day’ that is slightly longer 

than 24 hours for most people. Its sensitivity to light enables it to stay in step with the 

24-hour day/night cycle. 

• Almost every aspect of human functioning (physical or mental) undergoes daily cycles 

that are influenced by the circadian body clock. 
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• The daily minimum in core body temperature corresponds to the time in the circadian 

body clock cycle when people feel most sleepy and are least able to perform mental 

and physical tasks. This is sometimes called the Window of Circadian Low (WOCL) and 

it is a time of high risk for fatigue-related error. 

Shift Work

• Shift work can be defined as any duty pattern that requires a crewmember to be awake 

during the time in the circadian body clock cycle that they would normally be asleep. 

• The ability of the circadian clock to ’lock on’ to the 24-hour day/night cycle makes it 

resist adaptation to any pattern other than sleep at night. 

• The fact that the circadian body clock does not adapt fully to altered sleep/wake 

patterns has two main consequences; 

− duty days that overlap crewmembers’ usual sleep times (particularly all-night 

operations) tend to cause sleep restriction; and 

− crewmembers who are working through the window of circadian low (WOCL) can 

be expected to be sleepy and have to make additional effort to maintain their 

performance. 

• The further sleep is displaced from the optimum part of the circadian body clock cycle, 

the more difficult it becomes for crewmembers to get adequate sleep. 

• In scheduling, the frequency of recovery breaks (at least 2 consecutive nights of 

unrestricted sleep) needs to reflect the rate of accumulation of sleep debt 

Jet Lag

• Flying across time zones exposes the circadian body clock to sudden shifts in the 

day/night cycle. Because of its sensitivity to light and (to a lesser extent) social time 

cues, the circadian body clock will eventually adapt to a new time zone. 

• The rate of adaptation depends on the number of time zones crossed, the direction of 

travel (faster after westward flights) and the extent to which the circadian body clock is 

exposed to the 24-hour cues in the new time zone (outdoor light, sleeping and eating on 

local time, etc). 

• Layovers of 24-48 hours are not long enough to allow the circadian body clock to adapt 

to local time. 

• Different types of long haul trip patterns affect the circadian body clock in different ways. 

− Sequences of back-to-back trans-meridian flights that do not return to the domicile 

time zone for long periods of time tend to cause the circadian body clock to drift on 

its innate cycle. On return to the home time zone, additional days are needed to 

readapt to local time. 

− Sequences of out-and-back transmeridan flights that return to the home time zone 

on alternate layovers seem to enable the circadian body clock to remain 

synchronized to the home time zone. 

− On trips that include longer periods in the destination region, for example several 

days of local flying before the return flight home, the circadian body clock begins to 

adapt to the destination time zone. This may improve layover sleep. On the other 

hand, on return to the home time zone, additional days are needed to readapt to 

local time. 

• On long haul layovers, sleep is affected by competition between physiological 

processes (the homeostatic sleep drive and the circadian biological clock) and a 

preference for sleeping during the local night. 

• Route-specific recommendations for personal fatigue mitigation strategies may be 

useful in FRMS training for long haul and ULR crewmembers. 
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Operational Note: 

How Much Sleep in 24 hours is Enough?

This common question is usually aimed at trying to get a ‘magic number’ for the minimum 

amount of sleep that a crewmember needs, or the minimum rest period that needs to be 

scheduled. From a sleep science perspective, the answer is ‘it depends on many factors, 

including individual differences’. Some of the things it depends on are: 

• Recent sleep history - one restricted sleep period is a smaller fatigue risk for a 

crewmember who is starting out well-rested than for a crewmember who has already 

accumulated a sleep debt; 

• The amount of sleep a crewmember needs to be fully-rested (which varies among 

crewmembers); 

• Whether the crewmember is likely to obtain good quality sleep during the restricted 

sleep period. (For example, is sleep at home, in an onboard crew rest facility, in a 

layover hotel? Does the sleep opportunity occur at an appropriate time in the circadian 

body clock cycle?); 

• Whether sleep is shortened because a crewmember has to stay awake for an extended 

time beforehand (increasing the homeostatic pressure for sleep and the risk of microsleeps prior to the sleep period); 

• Whether sleep is shortened because a crewmember has to stay awake for an extended 

time afterwards (increasing the homeostatic pressure for sleep and the risk of microsleeps prior to the next sleep period); 

• Whether the crewmember will be trying to work through times of increased circadian 

sleep drive (the early hours of the morning and mid-afternoon when the circadian body 

clock is adapted to local time); 

• The criticality of the tasks that a crewmember will be undertaking after the restricted 

sleep period; 

• Other defensive strategies that are in place to manage the safety risk if that 

crewmember is fatigue-impaired as a result of the restricted sleep period; and 

• When the opportunity will occur for recovery from the effects of the restricted sleep 

period (for example, is it the first in a series of restricted sleep periods, or is it followed 

by two unrestricted nights of recovery sleep?). 

From a safety perspective, the answer is that no single defensive strategy is 100% sure. 

(The same desire for simplicity is a risk with bio-mathematical models that define a ‘safety 

threshold’ for crewmember fatigue. For example, there is a tendency to believe that an 

operation is safe if it is predicted to be below the threshold, but unsafe if it is predicted to be 

above it.) In an FRMS, safety comes from having a data-driven multi-layered system of 

defenses to manage fatigue risk, not from a reliance on simple thresholds. The FRMS 

answer is – measure crewmember fatigue levels, do a risk assessment and implement 

controls and mitigations as needed. These processes are the subject of Chapters Five and 

Six. 
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3.0 FRMS POLICY AND DOCUMENTATION 

This Chapter works through what needs to be included in an FRMS policy, and through the 

documentation that has to be kept to describe the FRMS and record its activities. The policy and 

documentation define organizational arrangements that support the core operational activities of 

the FRMS (the FRM processes and the FRMS safety assurance processes). The linkages between 

policy and documentation and other FRMS components are outlined in Figure 3.1. 

The FRMS policy specifies the operator’s commitment and approach to the management of fatigue 

risk. In some cases, it may be appropriate to include the FRMS policy in an operator’s SMS policy, 

if this is acceptable to the regulator. However, it should be noted that ICAO Annex 6, Part I, 

Appendix 8 requires an operator to clearly define all elements of the FRMS in its FRMS policy. The 

operator’s FRMS policy must be able to be distinguishable from the general SMS policy to allow 

separate review. 

The FRMS documentation describes the components and activities of the entire FRMS. It makes it 

possible for the effectiveness of the FRMS to be audited (internally and externally) to check 

whether it is meeting the safety objectives defined in the FRMS policy. Maintaining the required 

documentation is one of the recommended functions of the Fatigue Safety Action Group 

Figure 3.1: Linkages between FRMS policy and documentation and other FRMS components 
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Annex 6, Part I, Appendix 8 

FRMS policy and documentation 

1.1 FRMS policy 

1.1.1 The operator shall define its FRMS policy, with all elements of the FRMS clearly 

identified. 

1.1.2 The policy shall require that the scope of the FRMS operations be clearly defined in the 

Operations Manual. 

1.1.3 The policy shall: 

a) reflect the shared responsibility of management, flight and cabin crews, and other 

involved personnel; 

b) clearly state the safety objectives of the FRMS; 

c) be signed by the accountable executive of the organization; 

d) be communicated, with visible endorsement, to all the relevant areas and levels of 

the organization; 

e) declare management commitment to effective safety reporting; 

f) declare management commitment to the provision of adequate resources for the 

FRMS; 

g) declare management commitment to continuous improvement of the FRMS; 

h) require that clear lines of accountability for management, flight and cabin crews, 

and all other involved personnel are identified; and 

i) require periodic reviews to ensure it remains relevant and appropriate. 

Note: Effective safety reporting is described in Doc 9859, Safety Management 

Manual (SMM). 

1.2 FRMS documentation 

An operator shall develop and keep current FRMS documentation that describes and records: 

a) FRMS policy and objectives; 

b) FRMS processes and procedures; 

c) accountabilities, responsibilities and authorities for these processes and procedures; 

d) mechanisms for ongoing involvement of management, flight and cabin crew members, 

and all other involved personnel; 

e) FRMS training programs, training requirements and attendance records; 

f) scheduled and actual flight times, duty periods and rest periods with significant 

deviations and reasons for deviations noted; and 

g) FRMS outputs including findings from collected data, recommendations, and actions 

taken. 
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3.2 FRMS POLICY

The FRMS policy provides the umbrella under which the FRMS operates. Annex 6, Part I, 

Appendix 8 states that the FRMS policy must define the elements and scope of the FRMS 

and lists all aspects that it must cover. 

3.2.1 Scope of the FRMS 

ICAO Standards recommend that States allow an operator to choose whether it will 

use the FRMS to manage fatigue risk in all its operations, or only in designated 

specific types of operations (for example, only a particular fleet, only ULR 

operations, etc.). All operations not covered by the FRMS must operate under the 

applicable prescriptive flight and duty time limits (ICAO Annex 6, Part I, 4.10) 

As an operator’s familiarity and experience with FRMS builds, they may wish to 

expand the scope of the FRMS. This could be viewed as a natural evolution of the 

FRMS, and both the operator and the regulator need to give consideration to the 

procedures that would govern expanding the scope of an FRMS. The following text 

boxes show examples of statements of the scope of an FRMS. 

Example 1: 

Airline A - large international carrier with 11 different fleet types. 

In Example 1, the Flight Operations Manual initially lists the entire B-777 fleet and 

Ultra-Long Range (ULR) flights on the B-787, and only includes pilots. 

Subsequently, Airline A decides that it wants to add its A-330 fleet to the FRMS. 

With approval from the regulator, the A-330 fleet can be added to the list in the 

Flight Operations Manual that identifies operations covered by the FRMS, without 

requiring a change to the FRMS policy statement. This change makes the Fatigue 

Safety Action Group responsible for establishing FRMS processes to identify 

fatigue hazards in the A-330 operations, assess the risks, and develop and 

implement controls and mitigations. FRMS safety assurance processes also need 

to be established to monitor the effectiveness of the FRMS in managing fatigue 

risk in the A-330 operations. 

The addition of cabin crewmembers to the FRMS would require an amended policy 

statement, as follows. 

‘The FRMS for Airline A will apply to all operations as specifically identified in the 

Flight Operations Manual (FOM). All other operations will be conducted under the 

prescriptive flight and duty time regulations.’ 

‘The FRMS for Airline A will apply to all operations as specifically identified in the 

Flight Operations Manual (FOM) and Cabin Operations Manual (COM). All other 

operations will be conducted under the prescriptive flight and duty time 

regulations.’ 
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Example 2: 

Airline B - domestic carrier operating both scheduled and charter operations with 3 

fleet types. Airline B chooses to operate its charter operations under FRMS and to 

operate its scheduled operations under the prescriptive flight and duty time 

regulations. 

Example 3: 

Airline C - two airplane on-demand carrier that chooses to cover all its operations 

under FRMS. 

3.2.2 Things that the FRMS Policy Must Cover 

ICAO Annex 6, Part I, Appendix 8, Section 1.1.3 states that the FRMS policy must: 

a) reflect the shared responsibility of management, flight and cabin crews, and 

other involved personnel; 

b) clearly state the safety objectives of the FRMS; 

c) be signed by the accountable executive of the organization; 

d) be communicated, with visible endorsement, to all the relevant areas and 

levels of the organization; 

e) declare management commitment to effective safety reporting; 

f) declare management commitment to the provision of adequate resources for 

the FRMS; 

g) declare management commitment to continuous improvement of the FRMS; 

h) require that clear lines of accountability for management, flight and cabin 

crews, and all other involved personnel are identified; and 

i) require periodic reviews to ensure it remains relevant and appropriate. 

Management is primarily responsible for the management of fatigue risk because it 

controls the activities of personnel and the distribution of resources in the 

organization16. The FRMS is an organizational system that enables management 

to meet that responsibility. However, an FRMS can only be effective if all 

stakeholders are aware of their responsibilities and have the commitment, skills 

and resources to meet those responsibilities. 

 

16 ICAO Safety Management Manual (Doc 9859) 

‘The FRMS for Airline B will apply to all flight crew members in all charter aircraft 

operations.’ 

‘The FRMS for Airline C will apply to all flight crew members in all operations.’ 
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The particular nature of crewmember fatigue as a safety hazard also makes 

shared responsibility essential. Fatigue is affected by all waking activities, not only 

work demands - sometimes described as a ‘whole-of-life issue’ (Chapter Two). For 

example, crewmembers have personal responsibility because they can choose the 

amount of time they spend trying to sleep during available rest breaks, and choose 

when to use personal fatigue mitigation strategies (Chapter Four). In addition, their 

cooperation is vital for voluntary reporting of fatigue hazards, and when fatigue 

levels need to be measured for FRM processes (Chapter Four) and FRMS safety 

assurance processes (Chapter Five). Crewmembers’ willingness to cooperate will 

depend on their confidence that the operator is committed to the principles of an 

effective safety reporting culture (Chapter One). 

Like SMS, the Accountable Executive when signing the FRMS policy accepts 

accountability for the FRMS, either directly or through supervision and 

management of others, including those to whom the Accountable Executive has 

delegated responsibility. 

The safety objectives in the FRMS policy specify what the operator wants the 

FRMS to achieve. To track whether the FRMS is meeting these objectives, its 

performance needs to be monitored. Examples of safety performance indicators 

and targets that can be used to measure how well the FRMS is meeting the safety 

objectives can be found in Chapter Four and Chapter Five. 

The FRMS policy needs to be reviewed periodically by the operator, to ensure that 

it is adequate to meet changing operational demands. In addition, it should be 

subject to periodic review by the regulator. 
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3.3 EXAMPLES OF FRMS POLICY STATEMENTS

The following examples are intended to be used as guidance, not templates. Each operator 

needs to develop an FRMS appropriate their specific organizational context and operational 

needs. 

3.3.1 FRMS Policy Statement for a Major Air Carrier 

[Insert Company Name] Fatigue Risk Management Policy

As a commitment to the continuous improvement of safety, X Company has an FRMS to manage fatigue-related 

risks. 

This Fatigue Risk Management System (FRMS) applies to the operations as defined in the Flight Operations and Cabin

Operations Manuals. All other operations will operate under the prescriptive flight and duty time regulations. The FRMS

Manual describes the processes used for identifying fatigue hazards, assessing the associated risks, and developing,

implementing, and monitoring controls and mitigations. The FRMS Manual also describes the safety assurance processes used

to ensure that the FRMS meets its safety objectives, and how the FRMS is integrated with our industry‐leading SMS programs.  

Under this policy:

Management is responsible for:  

• Providing adequate resources for the FRMS;

• providing adequate crewing levels to support rosters that minimise fatigue risk;

• providing flight and cabin crew with adequate opportunity for recovery sleep between duties;

• creating an environment that promotes open and honest reporting of fatigue related hazards and incidents;

• providing fatigue risk management training to flight, cabin crew and other FRMS support staff;  

• demonstrating active involvement in and understanding of the FRMS;

• ensuring that the fatigue risks within their area(s) of responsibility are managed appropriately;  

• regularly consulting with flight and cabin crew regarding the effectiveness of the FRMS; and  

• demonstrating continuous improvement and providing annual review of the FRMS.

Flight and cabin crew are required to:  

• make appropriate use of their rest periods (between shifts or periods of duty) to obtain sleep;   

• participate in fatigue risk management education and training;  

• report fatigue‐related hazards and incidents as described in the FRMS Manual;  

• comply with the Fatigue Risk Management Policy;

• inform their manager or supervisor immediately prior to or during work if:

o they know or suspect they or another crew member are suffering from unacceptable levels of fatigue; or  

o they have any doubt about their or another crew member’s capability to accomplish their duties.

Fatigue Risk Management must be considered a core part of our business as it provides a significant opportunity to improve

the safety and efficiency of our operation and to maximise the well being of our staff.

Policy authorised by:

(Signed) ___________________________________

Insert Title (Accountable Executive)

Date:  __________________________
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3.3.2 FRMS Policy Statement for a Small Operator Providing Medical Evacuation 

Services 

[Insert Company Name] Fatigue Risk Management Policy 

The unique challenges that we face in our international medical evacuation operations here at [Insert Company 

Name] include 24 hour on-call schedules, a need for immediate response in all weather conditions, and many flights 

landing at unprepared locations. These challenges require our flight crews to perform at the highest levels of 

competence and professionalism at all times. They also mean that we are exposed on a regular basis to elevated 

fatigue risks, which are best managed through a Fatigue Risk Management System (FRMS). 

We need to manage these risks carefully in order to make consistently sound decisions, particularly to balance the 

critical needs of patients with the requirement for safe operations. This can only be achieved through the shared 

responsibility and commitment of management, crew members (pilots, doctors and nurses) and our support staff 

(e.g. crew schedulers) to ensure our fatigue risks remain acceptable. 

[Insert Company Name] will ensure that management, crew and support staff, and all other relevant personnel are aware of:

• the potential consequences of fatigue within our company;

• the unique challenges and fatigue risks confronting our staff due to the nature of our operations;

• the importance of reporting fatigue‐related hazards; and

• how to best manage fatigue.

To achieve this we have developed specific policies and procedures within our Safety Management System (SMS) for the

management of fatigue risks. These are documented in the FRMS sections of our SMS Manual and apply to all operational

staff.  

Management are responsible for:  

• appropriately resourcing the SMS;

• providing adequate crewing levels to support rosters that minimise fatigue risk;

• providing crew with adequate opportunity for recovery sleep between duties;

• creating an environment that promotes open and honest reporting of fatigue related hazards and incidents;

• providing fatigue risk management training to crew and other support staff;  

• demonstrating active involvement in and understanding of our fatigue risks;

• regularly consulting with crew regarding the effectiveness of fatigue management; and  

• demonstrating continuous improvement and providing annual review of fatigue management.

Crew and support staff are required to:  

• make appropriate use of their rest periods (between shifts or periods of duty) to sleep;

• participate in fatigue risk management education and training;  

• report fatigue‐related hazards and incidents;  

• comply with the Fatigue Risk Management Policy and Practices as contained within our SMS;

• inform their manager or supervisor immediately prior to or during work if:

o they know or suspect they or another crew member are suffering from unacceptable levels of fatigue; or

o they have any doubt about their or another crew members capability to accomplish their duties.

• seek external support in accordance with our company policies and procedures to ensure, whenever 

possible, that third parties (e.g. Chief Pilot, Operations Manager) who are not part of your crew are used to 

support crew decision making. Whenever crewmembers have doubts about their fatigue risk they are 

requested to use the company’s 24-hour hotline. 

The effective management of fatigue is critical to ensuring that our company can deliver a quality service to our customers.  

Policy authorised by:

(Signed) ___________________________________

Insert Title Accountable Executive)

Date:  ___________________________
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3.4 FRMS DOCUMENTATION

The documentation describes all the elements of the FRMS and provides a record of FRMS 

activities and any changes to the FRMS. The documentation can be centralized in an FRMS 

Manual, or the required information may be integrated into an operator’s SMS Manual. 

However, it needs to be accessible to all personnel who may need to consult it, and to the 

regulator for audit. 

ICAO Annex 6, Part I, Appendix 8 requires that an operator must develop and keep current 

FRMS documentation that describes and records: 

a) FRMS policy and objectives; 

b) FRMS processes and procedures; 

c) accountabilities, responsibilities and authorities for these processes and procedures; 

d) mechanisms for ongoing involvement of management, flight and cabin crew members, 

and all other involved personnel; 

e) FRMS training program, training requirements and attendance records; 

f) scheduled and actual flight times, duty periods and rest periods with significant 

deviations and reasons for deviations noted; and 

g) FRMS outputs including findings from collected data, recommendations, and actions 

taken. 

As a way of meeting these requirements, it is recommended that an operator create a 

functional group that is responsible for coordinating the fatigue management activities within 

the organisation. Such a group is referred to here as the Fatigue Safety Action Group. The 

principle functions of the Fatigue Safety Action Group are to: 

• develop and maintain the FRMS documentation; 

• manage the FRM processes (Chapter Four); 

• contribute to the FRMS safety assurance processes (Chapter Five); and 

• be responsible for the FRMS promotion processes (Chapter Six). 

However, in order to ensure that the focused management of fatigue risks does not result in 

unintended consequences in overall risk management for a particular organisation, some of 

the functions of the Fatigue Safety Action Group as described here may in fact be 

undertaken by the SMS team or other functional groups within the organisation. Regardless 

of who undertakes these functions, the regulator will need to observe and monitor all of the 

functions required under an FRMS. 

The composition of the Fatigue Safety Action Group should reflect the shared responsibility 

of individuals and management by including representatives of all stakeholder groups 

(management, scheduling staff, and crewmember representatives) and other individuals as 

needed to ensure that it has appropriate access to scientific and medical expertise. It should 

operate under Terms of Reference that are included in the FRMS documentation and which 

specify the lines of accountability between the Fatigue Safety Action Group and the 

operator’s SMS. 

The size and composition of the Fatigue Safety Action Group will vary for different operators, 

but should be related to the size and complexity of the operations covered by the FRMS, and 

to the level of fatigue risk in those operations. In small operators, a single individual may 

represent more than one stakeholder group, for example the chief pilot may also be the 

primary scheduler. In very small operators, there may not even be a designated Fatigue 

Safety Action Group, simply extra items on the Safety Meetings agenda, as long as long as 

all fatigue risk management activities are documented. Larger airlines will have specialized 

departments that interact with the Fatigue Safety Action Group. 
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Appendix 8, paragraph 1.2 f) also requires that significant deviations in scheduled and actual 

flight times, duty periods and rest periods, and reasons for those significant deviations be 

recorded by operators. As an initial step, the Fatigue Safety Action Group, or other 

appropriate entity within the organisation, will need to identify through a risk assessment 

process, differences between scheduled and actual flight times, duty periods and rest 

periods that will be considered significant within the context of their specific operations. 

For example, identified significant differences may include: 

1. for a particular city pair, any occasion where actual flight time exceeds planned flight 

time by 30 minutes; 

2. for a particular trip, any occasion where actual duty time exceeds planned duty time by 

60 minutes; 

3. for a particular layover, any occasion where the rest period is reduced from the planned 

rest period by 60 minutes. 

As a result, the significant deviations should be used as indicators to help identify potential 

fatigue hazards (discussed in Chapter Four) and may also be used to monitor the 

performance of the FRMS itself (Chapter Five). Further, the Fatigue Safety Action Group will 

also be responsible for establishing a process for monitoring such significant deviations and 

documenting any subsequent actions taken. 

Such definitions will need to be provided to the regulator for their acceptance and it will be 

important that there is a clear understanding between the regulator and the operator as to 

what constitutes a significant deviation. The regulator may also use these to identify criteria 

for when the operator must notify them immediately. 

3.4.1 Example of Terms of Reference for a Fatigue Safety Action Group 

This example is designed to cover the needs of a large operator. This is not a 

template. Not all the items suggested here will be needed by every operator. Each 

operator needs to consider its operational and organizational profile in deciding the 

composition of the Fatigue Safety Action Group, its activities, and its interactions 

with other parts of the operator’s organization. 
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[Insert Company Name] Terms of Reference: Fatigue Safety Action Group (FSAG) 

Purpose 

The Fatigue Safety Action Group (FSAG) is responsible for coordinating all fatigue risk management activities at 

[insert Company name]. This includes responsibility for gathering, analyzing, and reporting on data that facilitates 

the assessment of fatigue-related risk among flight crewmembers. The FSAG is also responsible for ensuring that 

the FRMS meets the safety objectives defined in the FRMS Policy, and that it meets regulatory requirements. The 

FSAG exists to improve safety, and does not get involved in industrial issues. 

Terms of Reference 

The FSAG is directly responsible to the Senior VP Flight Operations and reports through the Departmental Safety 

organization. Its membership will include at least one representative of each of the following groups: 

management, scheduling, and crewmembers, with other specialists as required. 

The tasks of the FSAG are to: 

• develop, implement, and monitor processes for the identification of fatigue hazards; 

• ensure that comprehensive risk assessment is undertaken for fatigue hazards; 

• develop, implement, and monitor controls and mitigations as needed to manage identified fatigue hazards; 

• develop, implement, and monitor effective FRMS performance metrics; 

• cooperate with the Safety Department to develop, implement and monitor FRMS safety assurance processes, 

based on agreed safety performance indicators and targets; 

• be responsible for the design, analysis, and reporting of studies that measure crewmember fatigue, when such 

studies are needed for the identification of hazards, or for monitoring the effectiveness of controls and mitigations 

(such studies may be contracted out but the FSAG is responsible for ensuring that they are conducted with the 

highest ethical standards, meet the requirements of the FRMS, and are cost-effective); 

• be responsible for the development, updating, and delivery of FRMS education and training materials (these 

activities may be contracted out but the FSAG is responsible for ensuring that they meet the requirements of the 

FRMS and are cost-effective); 

• ensure that all relevant personnel receive appropriate FRMS education and training, and that training records are 

kept as part of the FRMS documentation; 

• develop and maintain strategies for effective communication with all stakeholders; 

• ensure that crewmembers and others receive response to their fatigue reports; 

• communicate fatigue risks and the performance of the FRMS to senior management; 

• develop and maintain the FRMS intranet site; 

• develop and maintain the FRMS documentation; 

• ensure that it has adequate access to scientific and medical expertise as needed, and that it documents 

recommendations made by these specialist advisors and the corresponding actions taken; 

• keeps informed of scientific and operational advances in fatigue risk management principles and practice; 

• cooperate fully with the regulator in relation to FRMS auditing; and 

• manage effectively and be accountable for FRMS resources. 

The FSAG will meet monthly. Minutes will be taken during meetings and distributed within 10 working days after 

each meeting. The FSAG will present an annual budget request in [designated part of the financial cycle] and an 

annual report of all expenditures. 
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4.0 FATIGUE RISK MANAGEMENT (FRM) PROCESSES 

4.1 INTRODUCTION TO FRM PROCESSES

This Chapter works through the basic steps for setting up FRM safety risk management 

processes, which are very similar to SMS safety risk management processes3

. The main 

difference is that SMS processes are designed to address all types of risks. FRM processes 

within an FRMS are specifically designed to manage the risks related to crewmember 

fatigue. 

FRM processes (represented in the blue box in Figure 4.1 below) are one part of the day-today operations of the FRMS. They are designed to enable the operator to achieve the safety 

objectives defined in its FRMS Policy, and are managed by the Fatigue Safety Action Group 

(Figure 4.1). 

Figure 4.1 Linkages between FRM processes and other FRMS components 

FRM processes need to: 

1. identify where fatigue is a hazard; and 

2. assess the level of risk that a given fatigue hazard represents; and 

3. if necessary, put in place controls and mitigation strategies, and monitor to make sure 

that they manage the risk at an acceptable level. 

 

3

 See IATA Introduction to Safety Management Systems (SMS), 2nd Edition. 
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To do this, FRM processes require different sorts of data, including: 

a) measures of the fatigue levels of crewmembers; and 

b) measures of operational performance. 

Examples of these types of measures are described later in this Chapter. The key is choosing the 

right combination of measures for each operation that is covered by the FRMS. However, just 

collecting data is not enough. Data analysis needs to be used to inform decisions made by the 

Fatigue Safety Action Group and others accountable for the FRM processes and for FRMS safety 

performance (Chapter Five). The ICAO requirements for FRM processes are as follows (Annex 6, 

Part I, Appendix 8). 

Annex 6, Part I, Appendix 8 

2. Fatigue risk management processes 

2.1. Identification of hazards 

An operator shall develop and maintain three fundamental and documented 

processes for fatigue hazard identification: 

2.1.1. Predictive 

The predictive process shall identify fatigue hazards by examining crew 

scheduling and taking into account factors known to affect sleep and 

fatigue and their effects on performance. Methods of examination may 

include but are not limited to: 

a) operator or industry operational experience and data collected on 

similar types of operations; 

b) evidence-based scheduling practices; and 

c) bio-mathematical models 

2.1.2. Proactive 

The proactive process shall identify fatigue hazards within current flight 

operations. Methods of examination may include but are not limited to: 

a) self-reporting of fatigue risks; 

b) crew fatigue surveys; 

c) relevant flight and cabin crew performance data; 

d) available safety databases and scientific studies; and 

e) analysis of planned versus actual time worked 

2.1.3. Reactive 

The reactive process shall identify the contribution of fatigue hazards to 

reports and events associated with potential negative safety 

consequences in order to determine how the impact of fatigue could have 

been minimized. At a minimum, the process may be triggered by any of 

the following: 

a) fatigue reports; 

b) confidential reports; 

c) audit reports; 

d) incidents; and 

e) flight data analysis events 
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2.2. Risk assessment 

An operator shall develop and implement risk assessment procedures that 

determine the probability and potential severity of fatigue-related events and 

identify when the associated risks require mitigation. 

2.2.1. The risk assessment procedures shall review identified hazards and link 

them to: 

a) operational processes; 

b) their probability; 

c) possible consequences; and 

d) the effectiveness of existing safety barriers and controls. 

2.3. Risk mitigation 

2.3.1. An operator shall develop and implement risk mitigation procedures that: 

a) select the appropriate mitigation strategies; 

b) implement the mitigation strategies; and 

c) monitor the strategies’ implementation and effectiveness. 
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Figure 4.2 – Summarizes the steps in FRM processes. 

1. Identify operation(s) to 

 which FRMS processes apply

2. Gather and analyse data

3. Identify hazards

4. Assess safety risk

6. Monitor effectiveness of 

 mitigations

5a. Select and implement 

 controls and mitigation

5b. Set safety performance 

 indicators 

No Effective Yes

Different operations (e.g., ULR operations, night 

flights, charter operations, or particular fleets, routes, 

crew bases, etc) have different causes of fatigue and 

may need different mitigations. 

Collect and analyze data and use available 

information on potential fatigue hazards. Decide how 

this applies to your operation. 

Gather additional data on your operation if necessary.

Identify the specific nature of the fatigue hazard(s) that 

may need to be managed.

Conduct a safety risk assessment for each identified 

hazard. 

Decide which risks require mitigation

Implement appropriate mitigation strategies and 

communicate them to all relevant personnel. 

Set safety performance indicator(s), to be able to assess 

whether the mitigation strategies are delivering the 

required level of risk reduction.

If mitigation strategies perform to an acceptable standard, 

they become part of normal operations and are monitored 

by the FRMS safety assurance processes.

If mitigation strategies do not perform to an acceptable 

standard, then re-enter the FRM processes at the 

appropriate step

FRMS Assurance 

Processes
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4.2 FRM PROCESSES STEP 1: IDENTIFY THE OPERATIONS COVERED

ICAO Standards stipulate that States should allow an operator to choose whether it will use 

the FRMS to manage fatigue risk in all its operations, or only in specific types of operations 

(for example, only a particular fleet, only ULR operations, etc.). It is important that the 

operator clearly identifies to which operations the FRMS pertains. 

Further, as described in Chapter 2, different types of flight operations can involve different 

causes of crewmember fatigue and may require different controls and mitigation strategies to 

mitigate the associated risks. Within its FRMS, an organization may need to develop 

multiple sets of different FRMS processes for different operations, and again these should be 

clearly identifiable. On the other hand, in some cases it will be possible to include multiple 

types of operations under one set of FRM processes. 

4.3 FRM PROCESSES STEP 2: GATHER DATA AND INFORMATION

In Step 2, the Fatigue Safety Action Group gathers required data and information to be 

confident that they can identify the likely fatigue hazards in operations that are covered by 

the FRM processes. To do this, the group needs to have a good understanding of the 

operational factors that are likely to cause crewmember fatigue. 

To illustrate some of the considerations in different operations, Figure 4.3 compares flight 

and duty times in daytime short haul, domestic night cargo, and long haul operations studied 

by the NASA Fatigue Program. 4

 

Figure 4.3: 

Average flight, duty, and rest periods in a sample of daytime short haul, domestic night 

cargo, and long haul operations. 

 

4 Gander PH, Rosekind MR, Gregory KB (1998). Flight crew fatigue IV: a synthesis. Aviation, Space and 

Environmental Medicine 69 (9): B49-B60. 
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The daytime short haul operations (2-person crews) had the longest daily duty hours, 

averaged 5 flights per day, and had the shortest rest periods. However, they crossed a 

maximum of 1 time zone per 24 hours and the rest breaks occurred at night, during the 

optimal part of crewmembers’ circadian body clock cycle for sleep. The main causes of 

fatigue identified in this scientific study were: 

• restricted sleep caused by short rest periods and early duty report times; and 

• high workload, flying multiple sectors in high density airspace across long duty days. 

The domestic night cargo operations (2 pilots, 1 flight engineer) had the shortest duty 

periods, averaged 3 flights per duty period, and had longer rest periods than the short haul 

operations. They also crossed a maximum of 1 time zone per 24 hours. However, the night 

cargo crewmembers’ rest periods occurred during the day and their circadian body clocks 

(tracked by their core body temperature rhythms) did not adapt to this pattern. The main 

causes of fatigue identified in this scientific study were: 

• shorter, less restorative sleep during the day; and 

• being required to work at night, at the time in the circadian body clock cycle when selfrated fatigue and mood were worst, and when additional effort would be required to 

maintain alertness and performance. 

The long haul operations (2 pilots, 1 flight engineer) had long duty periods, but averaged 

only 1 flight per duty period and had the longest rest periods. However, every layover was in 

a different time zone, with a maximum of 8 time zones crossed per 24 hours. The 

crewmembers’ circadian body clocks (tracked by their core body temperature rhythms) did 

not adapt to the time zone changes or to the non-24-hour duty/rest pattern (averaging 10 

hours of duty and 25 hours of rest). The main causes of fatigue identified in this scientific 

study were: 

• long periods of wakefulness (average 20.6 hrs) associated with duty days (there were 

no onboard crew rest facilities); and 

• on some flights, having to operate the aircraft at the time in the circadian body clock 

cycle when self-rated fatigue and mood were worst, and additional effort was required 

to maintain alertness and performance; and 

• split sleep patterns and short sleep episodes on layovers (usually some sleep at local 

night and some at body clock night); and 

• on some trip patterns, the circadian body clock drifted away from crewmembers’ 

domicile time zone. As a result, additional time for circadian re-adaptation was needed 

for full recovery after the trip. 

These examples illustrate a fundamental principle in FRMS - that flight and duty time 

limitations do not capture all the causes of fatigue, which are different in different types of 

operations. 

Table 4.1 summarizes the different duty-related causes of fatigue identified in these studies. 

They pre-dated ULR flights and all involved scheduled operations. The very long duty days 

in ULR operations might be expected to cause fatigue, but the use of augmented crews and 

the availability of onboard crew rest facilities for in-flight sleep are important mitigation 

strategies. Unscheduled operations pose particular challenges, because it is hard to plan 

sleep when you do not know when you have to work, or for how long. 
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Table 4.1: Summary of Identified Work Related Fatigue Causes (from NASA field studies 18

Type of Operations 

Cause of Fatigue Hazard Domestic 

Short Haul 

Domestic 

Night Cargo 

Long Haul 

Restricted sleep due to short rest periods X 

Restricted sleep due to early duty report 

times 

X 

Multiple high workload periods across the 

duty day 

X 

Multiple sectors X X 

High density airspace X 

Long duty days X X 

Extended wakefulness on duty days X 

High workload during circadian low X X 

Shorter sleep periods at wrong times in the 

circadian cycle 

 X X 

Circadian disruption (due to night work) X X 

Split sleep patterns and short sleep episodes 

on layovers 

 X X 

Circadian disruption (due to crossing multiple 

time zones) 

 X 

Circadian drift (changes in circadian pattern) 

following extended patterns 

 X 

Note: These are the causes of fatigue identified in these particular studies, not an 

exhaustive list. 

Other potential causes of work-related fatigue include: 

• additional tasks that are performed immediately prior to a flight or at intermediate points 

during a series of flights; 

• high total duty time and flight time over specified periods (per month, per year), which 

increases the risk of cumulative fatigue; 

• not having the opportunity for adequate recovery sleep after one trip (or set of 

consecutive duties) before starting the next trip; and 

• other related tasks that crew members may be required to perform before or after flight 

duty, for example training activities, administrative duties, or baggage loading and 

unloading. 

When FRM processes are being set up, it is not always necessary to go out and gather new 

data for Step 2. It may be possible to identify potential fatigue hazards based on information 

and operational experience from similar types of operations flown by the operator or other 

carriers, or from published scientific studies of fatigue in similar operations. This is illustrated 

at the end of the Chapter, in the example on how to set up FRM processes for a new ULR 

route. 
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For existing routes being moved into the FRMS, data that is already routinely collected by 

the operator can be analyzed to help identify fatigue hazards (from various sources), for 

example the use of captain’s discretion, on-time performance, violations of prescriptive flight 

and duty time rules, level of sickness absences, and standby usage, or Aviation Safety 

Reports (ASR’s) that mention fatigue. It should be noted that it is a requirement of the 

FRMS SARPs (Annex 6, Part I, Appendix 8, 1.2 g) that the operator collects data on 

significant deviations to scheduled and actual flight times and duty periods, with the reasons 

for these significant deviations (previously discussed in Chapter Three). 

Once the FRM processes become fully operational, data collection and analysis are part of 

the operator’s day-to-day function, so a range of data will be available routinely for Step 2. In 

addition, the Fatigue Safety Action Group may sometimes decide to undertake non-routine 

data collection to better understand specific fatigue hazards (for example, a one-off fatigue 

survey at a crew base, or a targeted monitoring study on a route where fatigue is identified 

as a concern). Different types of information and data that can be collected are described in 

the following sections and in Appendix B. 

4.4 FRM PROCESSES STEP 3: HAZARD IDENTIFICATION

ICAO Annex 6, Part I, Appendix 8 requires that an operator develop, maintain, and 

document three types of processes for fatigue hazard identification: 

1. predictive processes; 

2. proactive processes; and 

3. reactive processes. 

All of these processes gather various kinds of information and data to continuously monitor 

the levels of fatigue risk in the operation(s) covered by the FRMS. These processes enable 

the Fatigue Safety Action Group to make data-driven decisions ‘based upon scientifically 

valid principles and measurements’ as stated in the ICAO definition of FRMS. 

As already mentioned, various types of data are involved including measures of operational 

performance, which operators are familiar with, and measures of the fatigue levels of 

crewmembers, which will be less familiar to most operators. The following sections and 

Appendix B provide guidance about measuring crewmember fatigue. Interpreting crew 

fatigue data also requires expertise. On some occasions, it may be appropriate for the 

Fatigue Safety Action Group to seek external scientific advice in this area. However, it is also 

possible for an operator to develop in-house expertise in fatigue data collection and analysis. 

This usually involves a ‘fatigue champion’ who is interested and motivated to develop skills 

as required. The complexity of operations and the level of fatigue risk need to be considered 

evaluating the need for, and level of, expert advice. 

4.4.1 Predictive Hazard Identification Processes 

In an FRMS, predictive hazard identification focuses on establishing crew 

schedules and conditions that consider factors known to affect sleep and fatigue in 

order to minimise their potential future effects. ICAO Annex 6, Part I, Appendix 8 

lists three possible ways of doing this: 

a) previous experience (of the operator or others in the industry); 

b) evidence-based scheduling practices; and 

c) bio-mathematical models. 

Note: See next page for expanded explanations of the above. 
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a) Previous Experience 

The collective experience of managers, schedulers, and crewmembers is an 

important source of information for identifying aspects of a proposed schedule that 

may be associated with increased fatigue. For example, crewmembers may 

recognize a particular destination within a proposed schedule as generating a high 

level of fatigue because of their past experience of regular delays there caused by 

heavy traffic. Schedulers may know that a particular city pairing regularly exceeds 

planned flying time. Management may organize for crew to stay in another hotel 

where noise is a known problem. 

Various information sources should be used. For existing operations, information 

about schedules may already be available that could be analyzed to check for 

potential fatigue hazards. Examples include the use of captain’s discretion, on-time 

performance, violations of prescriptive flight and duty time rules, standby usage, 

Aviation Safety Reports (ASR’s), and level of fatigue reports. 

When operational demands are changing, reliance on previous experience can 

have some limitations. Scheduling based only on previous experience may not 

give the most robust or innovative solutions for new situations. It may also be 

important to collect data on actual levels of crew fatigue, to check whether the 

lessons from previous experience are still valid in the new context. 

Another way to identify fatigue hazards related to scheduling, for existing or new 

routes, is to look for information on similar routes. This could include incident 

reports and crew fatigue reports, or published scientific research and other 

information available on similar routes flown by other operators. The amount of 

confidence that can be placed in this approach depends directly on how similar 

these other operations really are to the operation in which you are trying to identify 

fatigue hazards (see the ULR example at the end of this Chapter). 

b) Evidence-Based Scheduling Practices 

The value of operational experience can be enhanced when fatigue science is also 

applied in the building of schedules. This means considering factors such as the 

dynamics of sleep loss and recovery, the circadian biological clock, and the impact 

of workload on fatigue, along with operational requirements. Since the effects of 

sleep loss and fatigue are cumulative, evidence-based scheduling needs to 

address both individual trips (multiple, successive duty periods without extended 

time off), and successive trips across rosters or monthly bid-lines. The following 

are examples of general scheduling principles based on fatigue science. 

• The perfect schedule for the human body is daytime duties with unrestricted 

sleep at night. Anything else is a compromise. 

• The circadian body clock does not adapt fully to altered schedules such as 

night work. It does adapt progressively to a new time zone, but full adaptation 

usually takes longer than the 24-48 hours of most layovers. 

• Whenever a duty period overlaps a crewmember’s usual sleep time, it can be 

expected to restrict sleep. Examples include early duty start times, late duty 

end times, and night work. 

• The more that a duty period overlaps a crewmember’s usual sleep time, the 

less sleep the crewmember is likely to obtain. Working right through the usual 

night time sleep period is the worst case scenario. 

• requires working through the time in the circadian body clock cycle when selfrated fatigue and mood are worst and additional effort is required to maintain 

alertness and performance. 
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• Across consecutive duties with restricted sleep, crewmembers will accumulate 

a sleep debt and fatigue-related impairment will increase. 

• To recover from sleep debt, crewmembers need a minimum of two full nights 

of sleep in a row, when they are fully adapted to the local time zone. The 

frequency of rest periods should be related to the rate of accumulation of 

sleep debt. 

These sorts of principles can be used by an expert reviewer, for example by a 

scheduler trained in fatigue hazard identification, or by the Fatigue Safety Action 

Group, to develop evidence-based scheduling rules. The scientific basis for the 

scheduling rules should be recorded in the FRMS documentation. This approach 

can be validated, by monitoring the reported or estimated levels of fatigue across 

the schedules, using the tools described below and in Appendix B. Validation data 

can be used, in turn, to refine and improve evidence-based scheduling rules for an 

operation. 

c) Bio-Mathematical Models 

Bio-mathematical models begin life as computer programs used by scientists to 

test their current understanding of how factors like sleep loss, circadian rhythms, 

and workload interact to affect human alertness and performance. The modeling 

process begins by trying to write a program that can simulate a ‘developmental 

data set’ – for example self-rated fatigue and performance measured during a 

sleep loss experiment in the laboratory. If this works, then the model is used to 

predict a different situation. Data are then collected in this new situation (a 

‘validation data set’) and model predictions are tested against the new data. 

Scientific modeling is a continuous improvement process. As scientific tools, biomathematical models are accepted as being incomplete and transient. In scientific 

best practice, scientists continue designing new experiments to try to find out 

where their models fail. In this way, they find out where their current understanding 

is incomplete or possibly wrong. (This is a much more efficient way of increasing 

scientific knowledge than just doing random experiments.) 

A range of bio-mathematical models have been commercialized and are marketed 

as tools for predicting fatigue hazards relating to scheduling. There are also 

several models available in the public domain. Used properly, these models can be 

helpful tools in FRMS, because it is hard to visualize the dynamic interactions of 

processes like sleep loss and recovery, or the circadian biological clock. To use 

models properly requires some understanding of what they can and cannot predict. 

An important question to ask about any model is whether it has been validated 

against fatigue data from operations similar to those that you are interested in. 

Currently available models: 

• predict group average fatigue levels, not the fatigue levels of individual 

crewmembers; 

• do not take into account the impact of workload or personal and work-related 

stressors that may affect fatigue levels; 

• into account the effects of personal or operational mitigation strategies that 

may or may not be used by crewmembers (caffeine consumption, exercise, 

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• do not predict the safety risk that fatigued crewmembers represent in a 

particular operation, i.e., they are not a substitute for risk assessment (Step 4

in FRM processes– see below). Several available models try to predict safety 

risk by merging safety data from a range of operations in different industries, 

but their applicability to flight operations has not yet been validated. 

The most reliable use of currently available commercial models is probably for 

predicting relative fatigue levels – is the fatigue hazard likely to be greater on this 

schedule versus that schedule? However, model predictions should not be used 

without reference to operational experience, when making decisions about 

schedule design. On the other hand, data collected in the course of FRM 

processes could be a rich resource for improving the performance of biomathematical models, if model designers follow a continuous improvement 

philosophy. 

Note that in ICAO Annex 6, Part I, Appendix 8, it states that methods for predictive 

fatigue hazard identification may include but are not limited to: operator or industry 

operational experience and data collected on similar types of operations, evidencebased scheduling practices, and bio-mathematical models. In other words, none of 

these methods are required, and other methods may be used. 

4.4.2 Proactive Hazard Identification Processes 

In an FRMS, proactive hazard identification processes focus on monitoring fatigue 

levels in an operation. Because fatigue-related impairment affects many skills and 

has multiple causes, there is no single measurement that gives a total picture of a 

crewmember’s current fatigue level. 

For this reason, ICAO recommends using multiple sources of data for proactive 

hazard identification. To decide on which types of data to collect, the most 

important thing to consider is the expected level of fatigue risk. In other words, it is 

not a good use of limited resources to undertake intensive data collection with 

multiple measures on a route where the fatigue-related risk is expected to be 

minimal. Resources should be targeted towards operations where the risk is 

expected to be higher. 

The Importance of Collaboration

ICAO Annex 6, Part I, Appendix 8, requires that an operator’s FRMS Policy shall 

‘reflect the shared responsibility of management, flight and cabin crews, and other 

involved personnel’. 

The success of proactive processes (and of the FRMS) depends on the willingness 

of crewmembers to continue participating in data collection. This makes it 

important to consider the demands placed on crewmembers by different types of 

fatigue-related data collection (for example, measures such as filling out a 

questionnaire once, keeping a sleep/duty diary and wearing a simple device to 

monitor sleep every day before during and after a trip, doing multiple performance 

tests and fatigue ratings across flights, etc). 

The willingness of crewmembers to participate will also reflect their level of 

understanding of their roles and responsibilities in FRMS, and their confidence that 

the purpose of the data collection is to improve safety. Gathering fatigue-related 

data may involve monitoring crewmembers both on duty and off duty, because 

fatigue levels on duty are affected by prior sleep patterns and by waking activities 

outside of duty hours. 
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There are ethical considerations around issues such as the privacy of 

crewmembers, confidentiality of data, and whether crewmembers are really free to 

refuse to participate (voluntary participation is a requirement in scientific studies 

involving human participants). Many countries have specific legislation around 

privacy and workplace responsibilities for safety that may need to be considered, in 

addition to conditions specified in industrial agreements. 

Annex 6, Part I, Appendix 8 lists five possible methods of proactive fatigue hazard 

identification: 

a) self-reporting of fatigue risks; 

b) crew fatigue surveys; 

c) relevant flight crew performance data; 

d) available safety databases and scientific studies; and 

e) analysis of planned versus actual time worked. 

The following sections work through each of these methods in some detail. Keep in 

mind that these are options - they are not all required all of the time. 

a) Self-Reporting of Fatigue Risks 

Crewmembers’ reports about high fatigue levels or fatigue-related performance 

issues are vital to keep the Fatigue Safety Action Group informed about fatigue 

hazards in the day-to-day running of an operation. A series of fatigue reports on a 

particular route can be a trigger for further investigation by the Fatigue Safety 

Action Group. 

An effective fatigue reporting system requires an effective reporting culture. 5

 It 

needs to: 

• use forms that are easy to access, complete, and submit; 

• have clearly understood rules about confidentiality of reported information; 

• have clearly understandable voluntary reporting protection limits; 

• include regular analysis of the reports; and 

• provide regular feedback to crewmembers about decisions or actions taken 

based on the reports, and lessons learned. 

A fatigue report form (either paper-based or electronic) should include information 

on recent sleep and duty history (minimum last 3 days), time of day of the event, 

and measures of different aspects of fatigue-related impairment (for example, 

validated alertness or sleepiness scales). It should also provide space for written 

commentary so that the person reporting can explain the context of the event and 

give their view of why it happened. An example of a fatigue report form can be 

found in Appendix B. 

 

5

 See ICAO Doc 9859 Safety Management Manual. 
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b) Crew Fatigue Surveys 

Crew fatigue surveys are of two basic types: 

1. Retrospective surveys that ask crewmembers about their sleep and fatigue in 

the past. These can be relatively long and are usually completed only once, or 

at long time intervals (for example, once a year); and 

2. Prospective surveys that ask crewmembers about their sleep and fatigue right 

now. These are typically short and are often completed multiple times to 

monitor fatigue across a duty period, trip, or roster. They usually include 

measures such as sleepiness, fatigue, and mood ratings. 

Appendix B describes some standard fatigue and sleepiness measures (rating 

scales) that can be used for retrospective surveys, and others that can be used for 

prospective monitoring. These scales have been validated and are widely used in 

aviation operations. Using standard scales enables the Fatigue Safety Action 

Group to compare fatigue levels between operations (run by their own operator or 

others), across time, and with data from scientific studies. This can be helpful in 

making decisions about where controls and mitigations are most needed. 

Crew fatigue surveys can be focused on a particular operation or issue. For 

example, a series of fatigue reports about a particular trip might trigger the Fatigue 

Safety Action Group to undertake a survey of all crewmembers flying that trip 

(retrospective or prospective), to see how widespread the problem is. The Fatigue 

Safety Action Group might also undertake a survey (retrospective or prospective) 

to get crewmember feedback about the effects of a schedule change. 

Surveys can also be more general, for example providing an overview of fatigue 

across a particular aircraft fleet or operation type. Figure 4.4 shows an analysis of 

the effects of time of day and duty length on fatigue ratings at top of descent (using 

the Samn-Perelli fatigue scale - see Appendix B). These data come from the Air 

New Zealand FRMS and include 3181 ratings made across a 3-month period, at 

the end of 1-2 sector short haul duty days that stayed in the crewmembers’ 

domicile time zone (two-person crews). 6

 For short duty periods (2-4 hours) there is 

a clear time-of-day variation in how fatigued crewmembers feel at the top of 

descent, with highest average ratings between 03:00 and 06:00, and lowest 

average ratings between 15:00 and 18:00. In contrast, at the end of long duty 

periods (10-12 hours), fatigue ratings remain high from 00:00 to 09:00 and there is 

a second peak in fatigue between 12:00-15:00. These ratings show an interaction 

between time-on-task fatigue (duty duration) and the daily cycle of the circadian 

body clock. In addition, crew members who are at the end of a 10-12 hour duty 

period between 12:00 and 15:00 will have had their sleep restricted by an early 

duty report time. 

 

6

 Powell D, Spencer MB, Holland D, Petrie KJ (2008). Fatigue in two-pilot operations: implications for flight and duty 

time limitations. Aviation, Space and Environmental Medicine 79: 1047-1050. 
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Figure 4.4: Effects of time of day and duty length on fatigue ratings at top of 

descent in short haul operations across a 3-month period 

Compared to some other types of fatigue monitoring, crew fatigue surveys can be 

conducted relatively quickly and inexpensively to provide a “snapshot” of subjective 

fatigue levels and their potential causes. If a high proportion of crewmembers 

participate in a survey (ideally more than 70%), it gives a more representative 

picture of the range of subjective fatigue levels and opinions across the whole 

group. The information gathered in surveys is subjective (crewmembers’ personal 

recall and views), so getting a representative picture can be important for guiding 

the decisions and actions of the Fatigue Safety Action Group. 

c) Crew Performance Data 

Performance measurements provide objective data that can be used to 

supplement the subjective data collected in fatigue reports and survey responses. 

Currently, there are three main approaches to monitoring crewmember 

performance: 

1. simple tests developed in the laboratory, which measure aspects of an 

individual’s performance (for example, reaction time, vigilance, short-term 

memory, etc.); 

2. flight data analysis (FDA), which examines the relationship between identified 

elements of aircraft performance and 

3. pilot performance; and having trained flight deck observers rating the 

performance of crewmembers on the flight deck (for example, Line-Oriented 

Safety Audit). 

For monitoring crewmember fatigue levels during an operation, the first approach 

is currently the most practical. A range of objective performance tests are used in 

scientific research. Things to consider when choosing a performance test for 

measuring crewmember fatigue include the following. 
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1. How long does the test last? Can it be completed at multiple time points (for 

example, in the operations room during pre-flight preparations, near top of 

climb, near top of descent, and post-flight before disembarking from the 

aircraft), without compromising a crewmember’s ability to meet duty 

requirements? 

2. Has it been validated? For example, has it been shown to be sensitive to the 

effects of sleep loss and the circadian body clock cycle under controlled 

experimental conditions? 

3. Is the test predictive of more complex tasks, e.g., crew performance in a flight 

simulator? (Unfortunately, there is very little research addressing this question 

at present. 

4. Has it been used in other aviation operations, and are the data available to 

compare fatigue levels between operations? 

Appendix B describes a performance test that is commonly used to measure 

crewmember fatigue – the Psychomotor Vigilance Task or PVT. 7

There is considerable interest in finding ways to link crew member fatigue levels to 

FDA data particularly during approach and landing. FDA data has the advantages 

that it is routinely collected and is relevant to flight safety. The difficulty is that a 

multitude of factors contribute to deviations from planned flight parameters. To use 

FDA data as an indicator of crewmember fatigue would require demonstrating 

consistent changes in FDA data that are reliably linked to other indicators of 

crewmember fatigue (for example sleep loss in the last 24 hours, time in the 

circadian body clock cycle, etc). Research in this area is ongoing. 

Using trained flight deck observers to rate the performance of crewmembers on the 

flight deck is very labor-intensive and expensive. Having the observer present may 

also have an alerting effect and place additional demands on crewmembers. 

These factors currently limit the usefulness of this approach for proactive fatigue 

hazard identification in an FRMS 

d) Available Safety Databases and Scientific Studies 

More general guidance about fatigue hazards may be available from external 

safety databases, such as Aviation Safety Reports (ASRs) and Mandatory 

Occurrence Reports (MORs) maintained by safety authorities, or databases 

maintained by airline organizations or research institutions. Because safety events 

are relatively rare, databases that collect and analyze them are an important 

additional source of information that complements direct assessment of fatigue 

levels in the operation(s) covered by the FRMS. 

A fairly large amount of scientific research has been undertaken on crewmember 

fatigue in flight operations. Some of this is available on the web, for example many 

studies from the NASA Fatigue Countermeasures Program can be downloaded fre 

http://human-factors.arc.nasa.gov/zteam/fcp/FCP.pubs.html

 

7

 Balkin TJ, Bliese PD, Belenky G, Sing H, Thorne DR, Thomas M, Redmond DP, Russo M, Wesensten NJ (2004). 

Comparative utility of instruments for monitoring sleepiness-related performance decrements in the operational 

environment. Journal of Sleep Research, 13: 219-227. 
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This type of research tends to be costly and labour-intensive and not all types of 

aviation operations have been studied in depth. The particular value of these 

studies is in their use of more rigorous scientific approaches, which increases the 

reliability of their findings. The level of detail in some studies may be more than is 

needed for proactive identification of fatigue hazards. However, most reports and 

published papers have executive summaries or abstracts that outline the key 

findings. 

e) Analysis of Planned versus Actual Time Worked 

The planning of schedules and rosters based on fatigue science as well as 

operational requirements permits predictive identification of fatigue hazards 

(Section 4.4.1 above). However, numerous unforeseen circumstances can cause 

changes to planned schedules, for example weather conditions, volcanic ash, 

unexpected technical problems, or crewmember illness. Crewmember fatigue 

relates to what is actually flown, not what is planned. Thus another proactive 

approach for identifying fatigue hazards is to analyze actual schedules and rosters 

for factors such as on-time performance, exceedences of the flight and duty time 

limits specified in the FRMS, and schedule manipulation by individual 

crewmembers. 

Monitoring Crewmembers’ Sleep

Given the primary importance of sleep loss and recovery in the dynamics of 

crewmember fatigue, another valuable and commonly used method for proactive 

fatigue hazard identification is sleep monitoring. 

Sleep can be monitored in a variety of ways, all of which have advantages and 

disadvantages (for details, see Appendix B). 

• The simplest and cheapest method of monitoring sleep is to have 

crewmembers complete a daily sleep diary before, during, and after the trip(s) 

being studied. They are typically asked to record when they sleep, and to rate 

the quality of their sleep, as soon as possible after waking up. This can be 

done using a paper diary or an electronic device such as a Personal Data 

Assistant (PDA). 

• A more objective measure of sleep/wake patterns can be obtained by 

continuously monitoring movement, using an “actigraph”. This is a wristwatchlike device that is worn continuously (except when showering or bathing). 

Data on the amount of movement is recorded regularly (typically every 

minute) and is downloaded to a computer after several weeks, for subsequent 

analysis. Because actigraphs are not cheap (yet), usually only a sample of 

crewmembers on a given trip would have their sleep monitored in this way. 

Current systems also require a trained person to process and analyze the 

data. 

• In rare cases, where the expected fatigue risk is high or uncertain (for 

example in new types of operations), portable polysomnographic recordings 

may be used to monitor sleep both in-flight and during layovers. This involves 

applying electrodes to the scalp and face to record electrical signals coming 

from the brain (electroencephalogram or EEG), eye movements (electrooculogram or EOG) and chin muscles (electromyogram or EMG). 

Polysomnography is the “gold standard” method for evaluating sleep quality 

and quantity, but it is relatively invasive for participants and expensive both in 

terms of equipment and because it requires manual scoring and analysis by a 

trained technician. 
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Selecting Measures of Crewmember Fatigue

Several options have just been described for assessing crewmember fatigue levels 

in order to identify fatigue hazards. ICAO Annex 6, Part I, Appendix 8 is clear that 

the five methods it lists can be used – it does not say that they must be used, or 

that other methods cannot be used. The following general points are intended to 

help operators to decide which measures to use and when to use them. 

1. Fatigue-related impairment affects many skills and has multiple causes, so 

there is no single measurement that gives a total picture of a crewmember’s 

current fatigue level. 

2. The most important thing to consider in choosing fatigue measures is the 

expected level of fatigue risk. All measures require resources (financial and 

personnel) for data collection and analysis. Limited resources need to be used 

effectively to identify fatigue hazards and to help the Fatigue Safety Action 

Group prioritize where controls and mitigations are most needed. 

3. A core set of measures can be selected for routine monitoring. For example, 

crew fatigue reports and regular analysis of scheduling and rostering variations 

could be used for ongoing monitoring of fatigue hazards. 

4. An additional range of measures can be available to be used if a potential 

hazard is indentified and the Fatigue Safety Action Group decides that it needs 

more information about that hazard. Again, the measures selected need to 

reflect the expected level of risk. For example: 

a) A series of complaints about a particular layover hotel prompts a brief online survey of crewmembers using that hotel, to see how widespread the 

problem is and whether it merits action. 

b) A series of fatigue reports is received about a tag flight on the end of a 

particular trip. This prompts monitoring of the sleep, sleepiness, and 

fatigue ratings of crewmembers flying that trip, using sleep dairies and 

subjective rating scales. Data collection continues for a month, followed 

by data analysis, so that within 3 months the Flight Safety Action Group 

will have the information it needs to reach a decision and plan any 

necessary controls and interventions (for example, having another crew 

take the tag flight). 

c) An operator with limited long haul experience gets the regulators’ 

agreement to begin developing an FRMS in order to undertake ULR 

operations on a specified city pair. As part of gaining regulatory approval 

for the overall FRMS, the operator is required to undertake intensive 

monitoring of crewmember fatigue during the first 4 months of the 

operation. This includes monitoring sleep before, during, and after the trip 

using actigraphs and sleep diaries, as well as ratings of sleepiness and 

fatigue and PVT performance tests pre-flight, within 30 minutes of top of 

climb, before each in-flight rest period, within 30 minutes of top of 

descent, and post flight before leaving the aircraft. The regulator requires 

a report on the findings no later than 6 months after the launch of the 

operation. 

5. Balance needs to be maintained between gathering enough data for the 

Fatigue Safety Action Group to be confident about its decisions and actions 

and the additional demands that data collection can place on crewmembers 

(sometimes described in science as ‘participant fatigue’). 
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4.4.3 Reactive Hazard Identification Processes 

In an FRMS, reactive processes are designed to identify the contribution of 

crewmember fatigue to safety reports and events. The aim is to identify how the 

effects of fatigue could have been mitigated, and to reduce the likelihood of similar 

occurrences in the future. ICAO Annex 6, Annex 6, Part I, Appendix 8 lists five 

examples of triggers for reactive processes: 

a) fatigue reports; 

b) confidential reports; 

c) audit reports; 

d) incidents; and 

e) Flight Data Analysis (FDA) events (also known as Flight Operations Quality 

Assurance or FOQA). 

Depending on the severity of the event, a fatigue analysis could be undertaken by 

the Fatigue Safety Action Group, the operator’s safety department, or an external 

fatigue expert. The findings of any fatigue investigation should be recorded as part 

of the FRMS documentation. 

There is no simple test (such as a blood test) for fatigue-related impairment. To 

establish that fatigue was a contributing factor in an event, it has to be shown that; 

1. the person or crew was probably in a fatigued state; and 

2. the person or crew took particular actions or decisions that were causal in what 

went wrong; and 

3. those actions or decisions are consistent with the type of behaviour expected 

of a fatigued person or crew. 

To show that the person or crew were likely to be in a fatigued state, ideally you 

would have information about: 

• how much sleep they need to feel fully rested; and 

• how much sleep they had in the 24 hours before the accident (acute sleep 

loss); and 

• how much sleep they had in the 72 hours before the accident (cumulative 

sleep debt); and 

• how long they had been awake at the time of the event (extended 

wakefulness); and 

• whether their workload was unusually heavy or light leading up to and during 

the event; and 

• whether they were in a sleepy part of the circadian body clock cycle at the 

time of the event (early morning or mid-afternoon, body time); and 

• when they last had the opportunity for full recovery from sleep debt (at least 

two nights of unrestricted sleep in a row, fully adapted to the local time zone). 

This information generally has to be gathered after the event, based on the recall 

of the people involved, and should be confirmed where possible by anyone with 

whom they spent time leading up to the event. Where it is not possible to get this 

information, the duty history can give an idea of what opportunities the person or 

crew had for sleep. 
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There are no simple rules for interpreting this information (how much acute sleep 

loss do you need to be fatigue-impaired? how much cumulative sleep debt?). 

Transport Canada has proposed a method for fatigue investigation that provides 

useful guidance for answering these questions, and for deciding if the 

crewmember’s actions or decisions are consistent with the type of behaviour 

expected of a fatigued person or crew, although it has not yet been validated in 

aviation operations. This method is summarized in Appendix B. 

4.5 FRM PROCESSES STEP 4: RISK ASSESSMENT

Once a fatigue hazard has been identified, the level of risk that it poses has to be assessed 

and a decision made about whether or not that risk needs to be mitigated. Fatigue risk 

assessment follows SMS principles (combining risk probability and risk severity). It evaluates 

the potential for injury, equipment damage, or loss due to a fatigue hazard, and provides 

recommendations about management of that risk, as summarized in the following tables. 8

Table 4.2a: Defining Fatigue Risk Probability 

Fatigue Risk Probability 

Meaning 

Frequent Likely to occur many times (has occurred frequently) 5 

Occasional Likely to occur sometimes (has occurred infrequently) 4 

Remote Unlikely to occur, but possible (has occurred rarely) 3 

Improbable Very unlikely to occur (not known to have occurred) 2 

Extremely 

improbable Almost inconceivable that the event will occur 1 

 

8

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Table 4.2b: Defining Fatigue Risk Severity 

Fatigue Risk Severity 

Meaning 

Catastrophic • Multiple deaths 

• Equipment destroyed 

A 

Hazardous • A large reduction in safety margins, physical distress 

or a workload such that crewmembers cannot be 

relied upon to perform their tasks accurately or 

completely 

• Serious injury 

• Major equipment damage 

B 

Major • A significant reduction in safety margins, a reduction 

in the ability of crewmembers to cope with adverse 

operating conditions as a result of increase in 

workload, or as a result of conditions impairing their 

efficiency 

• Serious incident 

• Injury to persons 

C 

Minor • Nuisance 

• Operating limitations 

• Use of emergency procedures 

• Minor incident 

D 

Negligible • No signficant consequences E 

Table 4.2C: Fatigue Risk Assessment Matrix 

Fatigue Risk 

Risk Probability Risk Severity 

Catastrophic

A 

Hazardous 

B 

Major 

C 

Minor 

D 

Negligible 

E 

Frequent 5 5A 5B 5C 5D 5E 

Occasional 4 4A 4B 4C 4D 4E 

Remote 3 3A 3B 3C 3D 3E 

Improbable 2 2A 2B 2C 2D 2E 

Extremely 

Improbable 1 1A 1B 1C 1D 1E 
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Table 4.2d: ICAO Risk Tolerability Matrix 

Suggested Criteria Assessment Risk Index Suggested Criteria 

Intolerable Region 

5A, 5B, 5C 

4A, 4B, 

3A 

Unacceptable under the 

existing circumstances 

Tolerable 

Region 

5D, 5E, 

4C, 4D, 4E, 

3B, 3C, 3D 

2A, 2B, 2C 

Acceptable based on risk 

mitigation. May require 

management decision 

Acceptable 

Region 

3E, 

2D, 2E, 

1A 

1B, 1C, 1D, 1E 

Acceptable 

However, it should be noted that these tables are provided as general examples only. In 

reality, each operator must develop their own criteria for levels of severity and probability. 

There are no right and wrong criteria, but whatever criteria are identified, they must be 

agreed upon and widely understood by the people who will then use them to make risk 

assessments. Depending on an operator’s safety management structure, the Fatigue Safety 

Action Group may identify the severity and probability criteria, and then use these to assess 

the fatigue-related risks and the need for mitigation in an FRMS. 

4.6 FRM PROCESSES STEP 5: RISK MITIGATION

When it is decided that a particular fatigue hazard requires action, then controls and 

mitigations must be identified and implemented. The specific expertise of the Fatigue Safety 

Action Group should be used in the selection of these controls and mitigations. All involved 

personnel need to clearly understand the hazard and the controls and mitigations designed 

to reduce the associated risk. 
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Table 4.3 provides some examples of organizational-level controls and mitigations for 

managing fatigue hazards. A control is a system defence designed to manage specific 

elements of fatigue risk. (ICAO SSM) Mitigation is the use of the defence. These are 

examples only, not exhaustive lists. 

Fatigue Hazard Controls Mitigations 

Back-to-back night flights Scheduling rules do not permit 

back to-back night flights. 

Software is programmed to 

prohibit scheduling of back-to-back 

night flights. 

Reserve crew available to cover 

exceptional circumstances 

Lack of ULR crew in departure 

city base 

All flights scheduled >12 hours 

require evaluation of staffing levels 

at crew base in departure city. 

Established crew staffing policies 

to support operation and monitor 

staffing levels to ensure that policy 

requirements are being met 

Relocate additional crewmembers 

to departure city base. 

Ensure that sufficient reserve 

crews are available to support 

ULR flight schedules. 

Lack of ULR crew in en-route 

divert base 

Establish reserve crew staffing at 

en-route base to support 

diversions 

Reserve crew call-out 

Reports of inadvertent crew 

napping on the flight deck 

Scheduling rules, trip construction, 

rostering, crew augmentation 

policies to enable in-flight rest, 

improved onboard crew rest 

facilities 

Scheduling changes to improve 

layover sleep opportunities. 

Flight Operations Manual 

procedure for controlled flight deck 

napping developed 

Crewmembers not getting enough 

sleep in onboard rest facilities 

Pay attention to design of crew 

rest facilities when ordering 

aircraft. Retro-fit problem aircraft. 

Flight ops manual contains rules 

for organizing in-flight rest 

Provide crewmembers with 

education on how to obtain optimal 

in-flight sleep 

Captain’s discretion on the day 

allowed for organization of in-flight 

rest. 

Interrupted sleep periods in crew 

hotels 

Scheduling rules, trip construction, 

rostering 

Internal procedures to restrict crew 

contacts during rest periods 

Hotels required to provide 

segregated crew rest hotel areas, 

minimizing noise 

Landings at a confluence of 

circadian low, extended work 

period, and high work demands. 

Scheduling rules, trip construction, 

rostering 

Protocols for in-flight rest and 

controlled flight deck napping. 
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The effectiveness of implemented controls and mitigations must be assessed, which requires 

setting safety performance indicators such as the following. 

Schedule-related indicators:

• Number of flight deviations (or flight completion not accomplished) on specific city 

pairings, due to fatigue, lack of staff, medical emergencies, etc. 

• Number of bids for pairings identified as high fatigue risk (e.g. back-to-back night 

flights). 

• Number of crew duty day exceedences into allowable excesses (as determined through 

risk assessment. For example, longer than 14 hours.) 

• Number of flight duty periods determined to be “significantly” later than scheduled*. . 

• Number of flight duty periods longer than a specified number of hours without a rest 

break within the duty. 

• Number of flight times more than a specified number of minutes longer than planned 

(e.g., 30 or 60 minutes). 

• Number of flight duty periods starting within window of circadian low (WOCL). 

• Number of landings within the WOCL. 

• Number of duty periods with more than a specified number of flight sectors. 

• Number of duty periods with more than a specified number of aircraft changes. 

• Number of successive early wakeups, especially combined with long “sits” between 

flights or long duty days. 

• Number of reduced rest breaks within duties (by more than a specified number of 

minutes determined to be “significant”)*. 

• Number of reduced rest breaks between duties (by more than a specified number of 

minutes determined to be “significant”)*. 

• Number of reserve crew call-outs (on particular flights, at a particular crew base, etc). 

Note: * This indicator is a specific requirement of an FRMS, (Section 1.2 f, Appendix 8, 

Annex 6, Part I), and is discussed in Chapter Three. 

Proactive/reactive fatigue indicators:

• Measured data outside acceptable thresholds (e.g., sleepiness ratings, PVT scores, or 

inadequate layover sleep duration). 

• Numbers of fatigue reports (sorted in many ways such as by crew base, seat, 

augmented flights, fleet types, operational types, etc). 

• Number of fatigue-related incidents. 

• Number of fatigue-related FOQA events associated with a particular schedule for which 

fatigue reports have been received. 

• Absenteeism/fatigue calls. 

The implications of such safety performance indicators need to be considered within the 

context of the entire operation, to distinguish between acceptable and unacceptable risk. 

If the controls and mitigations perform to an acceptable standard (i.e., they bring the risk into 

the tolerable region – see Table 4.2d), they become part of normal operations and are 

monitored by the FRMS safety assurance processes. If the controls and mitigations do not 

perform to an acceptable standard, then it will be necessary to re-enter the FRM processes 

at the appropriate step. As indicated in Figure 4.2, this could require: gathering of additional 

information and data; and/or re-evaluation of the fatigue hazard and the associated risks; 
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and / or identification, implementation, and evaluation of new or revised controls and 

mitigations. 

4.7 EXAMPLE: SETTING UP FRM PROCESSES FOR A NEW ULR ROUTE

In 2005, recommended guidelines for ULR operations were developed by a Flight Safety 

Foundation consortium group– the Ultra Long Range Crew Alertness Steering Committee. 

This group identified ULR operations as scheduled operations that exceed 16 hours. This 

16-hour distinction for ULR operations has since become broadly accepted.

This example works through FRMS processes that could be used for establishing a new 

ULR operation (scheduled flight times in excess of 16 hours). It is developed from an actual 

safety case for a new ULR route that received regulatory approval, but it is an example not a 

recipe. The accepted approach for ULR operations is to evaluate each city pair to be flown. 9

Figure 4.5 summarizes the FRM processes, which are explained in more detail in the text. 

4.7.1 Step 1 – Identify the Operation 

The operation to which these FRM processes apply is a new ULR route between 

City A and City B (described here as the A-B-A route). 

4.7.2 Step 2 – Gather Data and Information 

Information and data are potentially available from two types of existing operations: 

long-haul operations that are similar but have flight times under 16 hours; and ULR 

operations already being flown by other operators. The relevance of the available 

information depends on how closely the existing operations resemble the proposed 

new ULR operation. The following factors need to be considered. 

• Crew complement and facilities for in-flight rest. 

• Crew domicile (if crewmembers are domiciled in the departure city and they 

have had sufficient time off since their last trans-meridian flight, it can be 

assumed that their circadian body clocks are adapted to domicile time). 

• Departure time of the outbound flight (local time and likely body clock time). 

• Outbound flight duration and time zones crossed. 

• Arrival time of the outbound flight (local time and likely body clock time). 

• Duration of the layover. 

• Departure time of the return flight (local time and likely body clock time). 

• Return flight duration and time zones crossed. 

• Arrival time of the return flight (local time and likely body clock time). 

• Depending on the actual city pairs being served, it may also be relevant to 

compare winter and summer schedules for take-off and landing times and 

flight durations. 

In this case, another operator has been flying a ULR trip between City C and City 

D. This existing operation has the same crew complement and similar departure 

times, flight durations, layover durations, and patterns of time zone crossings as 

the A-B-A route. As part of the regulatory approval process for the C-D-C route, 

the operator was required to conduct a 6-month operational validation, which 

included intensive monitoring of crewmember sleep and fatigue. 

 

9

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The operator generously makes these findings available for use in the A-B-A safety 

case, through an independent scientific team who were involved in the C-D-C data 

collection and analysis. (The expertise of the scientific team ensures that the 

findings are interpreted and applied to the A-B-A route in an appropriate manner.) 

Figure 4.5: FRM Processes in Setting up a New ULR route 

1. Identify operation(s) to 

 which FRMS processes apply

2. Gather and analyse data

3. Identify hazards

4. Assess safety risk

6. Monitor effectiveness of 

 mitigations

5a. Select and implement 

 controls and mitigation

5b. Set safety performance 

 indicators 

No Effective Yes

Bio-mathematical model simulations predict that, with two crews 

and in-flight sleep, fatigue risk is less than on some existing long 

haul routes.

City C-City D-City C ULR has flown daily for 4 years without 

fatigue-related incident.

Proactive: bio-mathematical model predictions are tested against 

the data from City C-City D-City C. Most reliable model is used to 

predict fatigue levels on City A-City B-City A route.

Proactive: existing fatigue surveillance methods plus enhanced 

monitoring during the first 4 months of the City A-City B-City A 

route.

Reactive: systems are in place for analysis of fatigue contribution 

to any safety events.

FRMS Assurance 

New ULR route City A-City B-City A

Route is very similar to an existing ULR route flown by another 

operator (City C-City D-City C) who collected and analyzed data. 

The other operator agrees to share information.

Multiple controls and mitigation strategies implemented 

(see text).

Data collection during first 4 months of operation to check biomathematical model predictions of fatigue levels.

Performance indicator – by 4th month of operation, no more 

fatigue reports per month than existing long haul routes.

Intensive fatigue monitoring during first 4 months of operation. 

Revert to routine monitoring if performance indicators are 

acceptable.
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4.7.3 Step 3 – Identify Hazards 

Predictive Processes

The operator already has experience with several long haul routes using the same 

aircraft and crew complement and with similar departure times and time zone 

crossings to the A-B-A route, but that remain under the 16-hour flight time limit that 

is used to define ULR. This experience has guided development of the operational 

plan for the A-B-A ULR route. 

Two bio-mathematical models are available that can be used to predict the likely 

levels of crewmember fatigue or alertness on the A-B-A route. The data collected 

on the C-D-C route are used to test how well these models can predict the sleep 

and fatigue of crewmembers before, during, and after ULR operations. 

One model (which has not been validated for aviation operations, but is sold for 

this use) makes the following predictions for the C-D-C route: that crewmember 

fatigue levels increase significantly across both the outbound and return flights; 

that layover sleep is too short to enable recovery before the return flight; and that 

fatigue levels are potentially unsafe by the end of both flights. These predictions 

are directly contradicted by PVT performance data and subjective sleepiness and 

fatigue ratings collected during the first 6 months of the C-D-C operation, which 

has flown daily without major incident for four years. The operational data and 

experience are considered more reliable than these bio-mathematical model 

predictions. 

On the other hand, the second model reliably predicts the duration of in-flight sleep 

on the C-D-C route (to within the range of variability seen among the 

crewmembers monitored). This model is chosen to predict crewmember alertness 

on the A-B-A route. 

Proactive Processes

The following proactive processes for identifying fatigue hazards are proposed for 

intensive monitoring during the first 4 months of the new operation, to validate the 

predictions about fatigue levels and fine tune the mitigation strategies, as needed. 

• Crewmembers are reminded about and encouraged to use existing fatigue 

reporting forms. 

• For the first month of the operation, a senior flight crewmember will be present 

in the Flight Operations Centre for the first and last few hours of every flight on 

the A-B-A route, to ensure rapid and appropriate management response to 

any fatigue-related issues arising. 

• For the first month of the A-B-A operation, a subset of crewmember 

volunteers is asked to complete a sleep and duty diary (with fatigue and 

sleepiness ratings) before, during, and after an A-B-A trip. These data will be 

compared with the same measures collected during the C-D-C operational 

validation. 

Other proactive fatigue monitoring processes that could be used include: 

• Asking all crewmembers to complete fatigue and sleepiness ratings at the top 

of descent on each flight, for the first month of the A-B-A operation. 

• Surveying all crewmembers after the A-B-A operation has been flown for 3 

months, to obtain an overview of their experience of fatigue and the 

effectiveness of different mitigation strategies (scheduling, in-flight rest 

facilities, layover hotels, etc). 
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• Having a subset of crewmember volunteers who wear actigraphs and 

complete sleep diaries before, during, and after a complete trip on the A-B-A 

route. In addition they would complete fatigue and sleepiness scales and 

undertake PVT performance tests at key times across each flight. These data 

would be compared with the same measures from the C-D-C operational 

validation. 

Reactive Processes

The operator has systems in place for analyzing the contribution of fatigue to 

safety reports and events, and for determining how to reduce the likelihood of 

similar events occurring in future. Special attention will be paid to ensuring that any 

fatigue reports or incidents from the A-B-A operation are analyzed quickly and 

appropriate action taken. 

4.7.4 Step 4 – Assess Safety Risk 

The bio-mathematical model used to predict crewmember alertness on the A-B-A 

route has previously been used to predict alertness on a range of 2-person and 3-

person long haul routes. These predictions indicate that minimum alertness levels 

on the A-B-A route are likely to be higher than on some existing long haul routes, 

notably 3-person westward return night flights with duty periods of about 14 hours, 

and long overnight flights with 2-person crews. 

Two sets of operational experience support the prediction that the A-B-A route 

does not pose excessive fatigue hazards: 1) the safety record of the C-D-C 

operation which has flown daily for four years; and 2) the A-B-A operator’s 

experience with similar long haul routes using the same aircraft and crew 

complement, but remaining under the 16-hour flight time limit. 

4.7.5 Step 5 – Select and Implement Controls and Mitigations 

In this example, the following controls and mitigation strategies are proposed for 

the A-B-A operation. 

• The aircraft chosen for the route has the best available on-board crew rest 

facilities. 

• All crewmembers flying the new operation are domiciled in the departure city. 

• All crewmembers flying the new operation receive specific education on 

personal and organizational strategies for managing fatigue on the A-B-A 

operation. This includes discussion on how to make best use of in-flight and 

layover sleep opportunities. 

• All crewmembers have protected time off duty to enable two full nights of 

sleep in the departure city time zone, so that they have the opportunity to 

begin the A-B-A operation fully rested. 

• There is a clear policy defining on-call arrangements and the provisioning of 

relief crew. 

• The flight crew includes 2 captains and 2 first officers, so that a single captain 

does not have sole command responsibility for entire ULR flights. This is in 

accordance with the Flight Safety Foundation ULR recommendations. 

• There is a clear policy on the distribution of in-flight rest opportunities, so that 

crewmembers can plan how best to use them. 

• Each crewmember has two rest opportunities per flight, to ensure that they 

have at least some rest time overlapping their normal sleep time and that they 

have a second opportunity to get some sleep if, for any reason, they are 

unable to sleep during their first in-flight rest period. 
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• Meals are available for flight crew on the flight deck if they wish, in order to 

maximize the amount of time during in-flight rest periods that is available for 

sleep. 

• The layover hotel has been carefully vetted to ensure that it provides excellent 

facilities for sleep, eating, and exercise. 

• A procedure is implemented between Flight Operations and the layover hotel 

to provide notification of delays without having to wake crewmembers. 

• There are clear procedures on the management of flight delays. 

• There are clear procedures on the management of flight diversions. 

• 

• The following safety performance indicators are identified: 

• Data collected during the first 4 months of the A-B-A operation will be 

compared with model predictions and with the same measures from the C-DC validation, to establish whether crewmember fatigue and alertness levels 

are in the range predicted. 

• By the fourth month of the A-B-A operation, the fatigue reporting rate 

(reports/flight segment) and average fatigue report risk level should be 

comparable to existing long haul routes. No ‘’intolerable” fatigue reports 

should be received (see Table 4.2.d). 

4.7.6 Step 6 – Monitor Effectiveness of Controls and Mitigations 

There is a defined validation period for the first four months of the operation that 

involves more intensive monitoring. The Fatigue Safety Action Group will have 

regular oversight of all data and fatigue reports coming in and will act in a timely 

manner when issues arise. 

At the end of the validation period, a report will be compiled and routine processes 

will be defined for fatigue risk monitoring and management on the A-B-A route. 

This report will be available to all interested parties. If the performance indicators 

are acceptable, the A-B-A operation will revert to routine monitoring. 

4.7.7 Linking to FRMS Safety Assurance Processes 

Normally, the FRM processes do not operate in isolation from the FRMS safety 

assurance processes (described in detail in the next Chapter). However, when 

setting up FRMS in an organization, or for a new type of operation, the data 

needed for FRMS safety assurance processes are not available before the 

operation(s) begin flying. This means that it is necessary to have a staged 

approach to FRMS implementation, which is described in Chapter Seven. 
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5.0 FRMS SAFETY ASSURANCE PROCESSES 

5.1 INTRODUCTION TO FRMS SAFETY ASSURANCE PROCESSES

The FRM processes described in Chapter Four are the part of the day-to-day FRMS 

operations that focuses on identifying fatigue hazards, assessing safety risks, putting in 

place controls and mitigation strategies, and monitoring their effectiveness. 

This Chapter works through the basic steps in FRMS safety assurance processes, which 

form another layer in an operator’s defenses against fatigue-related risk. FRMS safety 

assurance processes are also part of the routine operation of the FRMS, and they monitor 

how well the entire FRMS is functioning. They: 

• check that the FRMS is functioning as intended; 

• check that it is meeting the safety objectives defined in the FRMS policy; 

• check that it is meeting regulatory requirements; 

• identify where changes in the operating environment have the potential to increase 

fatigue risk; and 

• identify areas for improvement in the management of fatigue risk (continuous 

improvement of the FRMS). 

To do this, FRMS safety assurance processes use a variety of data and information as 

safety performance indicators that can be measured and monitored over time. Having a 

variety of safety performance indicators, plus a safety target for each, is expected to give 

better insight into the overall performance of the FRMS than having a single measure. 

Safety performance targets must fall in the tolerable region defined in the risk assessment 

process (see Section 4.5), and they may need to be revised as operational circumstances 

change. 10 

Figure 5.1 outlines the linkages between the FRMS safety assurance processes and other 

components of the FRMS. The information, data, and safety performance indicators from the 

FRM processes provide a source of information for the FRMS safety assurance processes. 

In addition, the FRMS safety assurance processes: 

1. use information and expertise from other sources, both from within the operator’s 

organization and external to it, to evaluate the functioning of the FRMS; and 

2. evaluate trends in safety performance indicators to identify emerging or changed 

hazards and refer these back to the FRM processes; and 

3. identify changes in the operating environment that could affect fatigue risk and refer 

these back to the FRM processes; and 

4. provide input about ways to improve the operation of the FRMS. 

 

10 See IATA Introduction to Safety Management Systems (SMS), 2nd Edition. 
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Figure 5.1: Linkages between FRMS assurance processes and other FRMS components 

Some of the FRMS safety assurance processes can be undertaken by the Fatigue Safety 

Action Group, while others (for example audits of the FRMS) would normally be undertaken 

by other units within the operator’s organization. The responsibility for different FRMS safety 

assurance activities may be distributed differently, depending on the size of the organization. 

For example, larger operators may have a separate FRMS safety assurance team and/or a 

designated FRMS safety assurance manager. Communication (in both directions) between 

the FRMS safety assurance processes and the SMS is necessary, since the safety 

performance of the FRMS will impact on overall safety performance. 

The ICAO requirements for FRMS safety assurance processes are as follows. 
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Appendix 8: 

3. FRMS Safety Assurance Processes 

3.1 The operator shall develop and maintain FRMS safety assurance processes to: 

a) provide for continuous FRMS performance monitoring, analysis of trends, and 

measurement to validate the effectiveness of the fatigue safety risk controls. The 

sources of data may include, but are not limited to: 

1) hazard reporting and investigations; 

2) audits and surveys; and 

3) reviews and fatigue studies; 

b) provide a formal process for the management of change which shall include but is 

not limited to: 

1) identification of changes in the operational environment that may affect FRMS; 

2) identification of changes within the organization that may affect FRMS; and 

3) consideration of available tools which could be used to maintain or improve 

FRMS performance prior to implementing changes; and 

c) provide for the continuous improvement of the FRMS. This shall include but is not 

limited to: 

1) the elimination and/or modification of risk controls have had unintended 

consequences or that are no longer needed due to changes in the operational 

or organizational environment; 

2) routine evaluations of facilities, equipment, documentation and procedures; and 

3) the determination of the need to introduce new processes and procedures to 

mitigate emerging fatigue-related risks. 
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Figure 5.2: FRMS Safety Assurance Processes 

1. Collect and review data.

2. Evaluate overall FRMS 

 performance.

3. Identify emerging fatigue 

 hazards

4. Identify changes affecting 

 FRMS

No Improve effectiveness of FRMS Yes

Use FRM processes to identify potential fatigue hazards 

arising from changes in the operating environment or 

organizational change. Assess risk, develop and implement 

controls and mitigations.

Do trends in performance indicators identify emerging or 

changed hazards? (Loop back to FRM processes to assess risk, 

develop and implement appropriate and relevant controls and 

mitigations.)

FRMS Process

FRMS safety assurance processes draw together internal and 

external sources of information to check that the FRMS is 

functioning as intended.

Evaluate FRMS effectiveness against safety performance targets 

and indicators. Is it meeting the safety objectives defined in the 

FRMS policy? Is it meeting regulatory requirements?

Review effectiveness of all FRMS components.

Review controls and mitigations. Effective controls require no 

change. Ineffective controls should be modified. Controls that 

are no longer needed can be eliminated.
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5.2 FRMS SAFETY ASSURANCE PROCESSES STEP 1: COLLECT AND REVIEW DATA

Step 1 involves bringing together and reviewing information gained through the FRM 

processes to examine the overall performance of the FRMS. Performance of the FRMS 

should be examined through indentifying a variety of safety performance indicators. These 

should include those specific to the FRMS as well as SMS safety performance indicators. 

Examples of safety performance indicators specific to an FRMS will include measures 

obtained through the FRM processes, such as: 

• The number of exceeded maximum duty days in operations covered by the FRMS; 

• The number of voluntary fatigue reports per month; 

• The average “fatigue call” rate by flight crews on a specific pairing (trip); 

• The ratio of fatigue reports from ULR operations covered by the FRMS to fatigue 

reports from the long haul operations covered by the prescriptive flight and duty time 

regulations. 

• Attendance at FRMS training sessions; 

• Results on FRMS training assessments; 

• The level of crew member participation in fatigue-related data collection; 

• The number times fatigue is identified as an organizational factor contributing to an 

event. 

ICAO Annex 6, Part I, Appendix 8 indicates that sources of data for monitoring the safety 

performance of the FRMS may include (but are not limited to): 

1. hazard reporting and investigations; 

2. audits and surveys; and 

3. reviews and fatigue studies. 

1. Hazard Reporting and Investigations

Trends in voluntary fatigue reports by crewmembers and others can provide valuable 

insights into the effectiveness of the FRMS. Safety events in which crewmember fatigue has 

been identified as a contributing factor will be less common than fatigue reports. However, 

regular review of these events may also highlight areas where functioning of the FRMS could 

be improved. The value of both these sources of information depends on using appropriate 

methods for analyzing for the role of fatigue (see Chapter 4 and Appendix B). 

2. Audits and Surveys

Audits and surveys can provide measures of the effectiveness of the FRMS without having 

to rely on fatigue levels being high enough to trigger fatigue reports or fatigue-related safety 

events (both of which are relatively rare events). 

Audits focus on the integrity of, and adherence to, the FRM processes. These audits should 

answer questions such as: 

• are all departments implementing the recommendations of the Fatigue Safety Action 

Group? 

• are crewmembers using mitigation strategies as recommended by the Fatigue Safety 

Action group? 

• is the Fatigue Safety Action Group maintaining the required documentation of its 

activities? 
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Audits can also periodically assess the effectiveness of the FRMS, for example by looking at 

the status of FRMS safety performance indicators and targets. 

Audits are ‘external’ to the Fatigue Safety Action Group, but may still be internal to the 

operator, i.e., conducted by other units within the organization. In addition, feedback from 

regulatory audits can provide useful information for FRMS safety performance monitoring. 

Another type of audit that can be used in this context is to have an independent scientific 

review panel that periodically reviews the activities of the Fatigue Safety Action Group, and 

the scientific integrity of their decisions. A scientific review panel can also provide the 

Fatigue Safety Action Group with periodic updates on new scientific developments relevant 

to the FRMS. 

Surveys can provide information on the effectiveness of the FRMS. For example they can 

document how schedules and rosters are affecting crewmembers, either by asking about 

their recent experiences (retrospective) or tracking them across time (prospective). Surveys 

for this purpose should include validated measures, such as standard rating scales for 

fatigue and sleepiness, and standard measures of sleep timing and quality (see Chapter 4

and Appendix B). Remember that a high response rate (ideally more than 70%) is needed 

for survey results to be considered representative of the entire group, and response rates 

tend to decline when people are surveyed too frequently (‘participant fatigue’). 

3. Reviews and Fatigue Studies

In general, safety reviews are used to ensure that safety performance is adequate during 

times of change, 11 for example during the introduction of a new type of operation or a 

significant change to an existing operation covered by the FRMS. 

A review would start by identifying the change (for example, moving a trip to a crew base in a 

different time zone, changes in on-board crew rest facilities, significant changes in the total 

trip, a change of equipment being used for the trip, etc). It would then evaluate the 

appropriateness and effectiveness of the FRMS activities relating to the change (for 

example, proposed methods for fatigue hazard identification, the risk assessment process, 

proposed controls and mitigations to address the fatigue hazard(s), and measures of their 

effectiveness to be used during the implementation of the change). 

Fatigue studies as part of FRMS safety assurance processes are undertaken when an 

operator is concerned about a broad fatigue-related issue for which it is appropriate to look 

at external sources of information. These could include the experience of other operators, 

industry-wide or State-wide studies, and scientific studies. These sources of information can 

contribute in situations when safety arguments based on the limited experience and 

knowledge within that operator may not be enough. Fatigue studies in this context are mainly 

used for gathering information about large-scale issues in FRMS, rather than for identifying 

specific fatigue hazards. 

FRMS Safety Performance Indicators

Trends in FRMS safety performance indicators are also an important source of information 

about the effectiveness of the FRMS. These may include indicators identified by the Fatigue 

Safety Action Group as part of the FRM processes (see Section 4.6). They may also include 

indicators that capture more global aspects of the safety performance of the FRMS, for 

example safety performance metrics within the operator’s SMS. 

 

11 See ICAO Doc 9859 Safety Management Manual. 
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5.3 FRMS SAFETY ASSURANCE PROCESSES STEP 2: EVALUATE FRMS PERFORMANCE

The aim of Step 2 is to validate the effectiveness of the fatigue controls and mitigations 

(ICAO Annex 6, Part I, Appendix 8). It involves analyzing the information gathered in Step 1 

to check whether: 

• all specified FRMS safety performance targets are being met; and 

• all specified FRMS safety performance indicators remain in the tolerable region defined 

in the risk assessment process (see Section 4.5); and 

• the FRMS is meeting the safety objectives defined in the FRMS policy; and 

• the FRMS is meeting all regulatory requirements. 

The following are examples of safety performance targets and indicators that could be used 

in FRMS safety assurance processes and that correspond with the safety performance 

indicators identified above (for additional examples see Section 5.8 below). 

• The length of the maximum duty days in operations covered by the FRMS does not 

exceed the limits defined in the FRMS policy. This is reviewed monthly by a computer 

algorithm and trends across time are evaluated every 3 months. 

• By the fourth month after the introduction of a new operation, there must be a stable low 

number of voluntary fatigue reports per month, or a clear downward trend in the number 

per month (allowing time for crewmembers and other affected personnel to adjust to the 

new operation). The Fatigue Safety Action Group is to provide a written report on the 

validation phase of the new operation, including analysis of all fatigue-related events 

and voluntary fatigue reports, and documentation of the corresponding adjustments 

made in fatigue controls and mitigations. 

• No specific pairing (trip) exceeds the average fatigue call rate by flight crews by more 

than 25%. 

• ULR operations covered by the FRMS do not attract any more fatigue reports than the 

long haul operations covered by the prescriptive flight and duty time regulations. 

• In the last quarter, designated management has provided adequate resourcing for the 

FRMS, as specified in the FRMS policy. 

• In the last quarter, the Fatigue Safety Action Group has met as often as is required in 

the FRMS policy and has maintained all the documentation of its activities that is 

required for internal and regulatory auditing. 

• All personnel responsible for schedule design and rostering have met annual FRMS 

training requirements as specified in the FRMS promotion processes. 

• Measures of the effectiveness of FRM training and education programs (see Chapter 6 

for examples). 

• Quarterly levels of absenteeism are below the target specified for each operation 

covered by the FRMS. 

When FRMS safety performance targets are not met or when safety performance indicators 

are not at an acceptable level, the controls and mitigations in use may need to be modified 

by re-entering the FRM processes at Step 2 or beyond (see Figure 4.2). It may also be 

appropriate to seek additional information from outside the organization (for example, by 

looking at fatigue studies). It may be necessary to undertake a review of compliance of 

crewmembers and other departments with the recommendations of the Fatigue Safety 

Action Group. It may also sometimes be necessary to review the functioning of the Fatigue 

Safety Action Group itself, to find out why the FRMS is not working as intended. 
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Figure 5.3 tracks a measure of the effectiveness of the Air New Zealand FRMS across 

time12. It shows that the percentage of pilots reporting duty-related fatigue occurring at least 

once a week has declined across a series of surveys conducted between 1993 and 2006. 

Figure 5.3: Declining reports of crewmember fatigue across successive Air New Zealand 

surveys 

 

12 Figure 5.3 is used by kind permission of Dr David Powell. 
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5.4 FRMS SAFETY ASSURANCE PROCESSES STEP 3: IDENTIFY EMERGING HAZARDS

Analysis of trends in safety performance indicators may indicate the emergence of fatigue 

hazards that have not previously been recognized through the FRM processes. For example, 

changes in one part of the organization may increase workload and fatigue risk in another 

part of the organization. Identifying emerging fatigue-related risks is an important function of 

FRMS safety performance processes, which take a broader system perspective than FRM 

processes. Any newly identified fatigue risk, or combination of existing risks for which current 

controls are ineffective, should be referred back to the Fatigue Safety Action Group for 

evaluation and management using FRM processes (risk assessment, design and 

implementation of effective controls and mitigations). 

5.5 FRMS SAFETY ASSURANCE PROCESSES STEP 4: IDENTIFY CHANGES AFFECTING FRMS 

In our dynamic aviation environment changes are a normal part of flight operations. They 

may be driven by external factors (for example, new regulatory requirements, changing 

security requirements, or changes to air traffic control) or by internal factors (for example, 

management changes, new routes, aircraft, equipment, or procedures). Changes can 

introduce new fatigue hazards into an operation, which need to be managed. Changes may 

also reduce the effectiveness of controls and mitigations that have been implemented to 

manage existing fatigue hazards. Step 4 of the FRMS safety assurance processes aims to 

identify when new hazards may be a result of change. 

ICAO Annex 6, Part I, Appendix 8 requires that an operator has FRMS safety assurance 

processes that provide a formal methodology for the management of change. These must 

include (but are not limited to): 

1. identification of changes in the operational environment that may affect FRMS; 

2. identification of changes within the organization that may affect FRMS; and 

3. consideration of available tools which could be used to maintain or improve FRMS 

performance prior to implementing changes. 

A change management process is a documented strategy to proactively identify and manage 

the safety risks that can accompany significant change in an airline1

. When a change is 

planned, the following steps can be followed. 

• Use the FRM processes to identify fatigue hazards, assess the associated risk, and 

propose controls and mitigations; 

• Obtain appropriate management and/or regulatory sign-off that the level of residual risk 

is acceptable. 

During the period of implementation of the change, use the FRMS safety assurance 

processes to provide periodic feedback to line managers that the FRMS is functioning as 

intended in the new conditions. An example would be having a validation period for a new 

ULR route, during which additional monitoring of crewmember fatigue is undertaken, 

together with more frequent assessment of FRMS safety performance targets and indicators. 

Documentation of the change management strategy in relation to fatigue management is 

also the responsibility of the Fatigue Safety Action Group. 

Changes in the operational environment may also necessitate changes in the FRMS itself. 

Examples include bringing new operations under the scope of the FRMS, collecting different 

types of data, adjustments to training programs, etc. The Fatigue Safety Action Group should 

propose such changes and obtain approval for them from appropriate management. 
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5.6 FRMS SAFETY ASSURANCE PROCESSES STEP 5: IMPROVE EFFECTIVENESS OF FRMS 

Ongoing evaluation by the FRMS safety assurance processes not only enables the FRMS to 

be adapted to meet changing operational needs, it also allows the FRMS to continuously 

improve the management of fatigue risk. In doing so, risk controls that have unintended 

consequences or that are no longer needed due to changes in the operational or 

organizational environment can be identified, then modified or eliminated through the FRM 

processes. Examples include: 

1. routine evaluations of facilities, equipment, documentation and procedures; and 

2. the determination of the need to introduce new processes and procedures to mitigate 

emerging fatigue-related risks. 

It is important that changes made to the FRMS are documented by the Fatigue Safety Action 

Group so that they are available for internal and regulatory audit. 

5.7 ASSIGNING RESPONSIBILITY FOR FRMS SAFETY ASSURANCE PROCESSES

To deliver effective oversight of the functioning of the FRMS, and to examine its functioning 

in relation to the SMS, the FRMS safety assurance processes need to operate in close 

communication with the Fatigue Safety Action Group, but with a degree of independence 

from it. The aim is to avoid the Fatigue Safety Action Group reviewing its own performance. 

Figure 5.4 describes an example of how responsibility for the FRMS safety assurance 

processes might be assigned in a large organization. 

In this example, the Fatigue Safety Action Group is accountable to the Safety Team for Flight 

Operations. The Safety Team for Flight Operations is accountable in turn to the Executive 

Safety Team. In Figure 5.4, these lines of accountability are indicated by heavy arrows. (In a 

large organization, there might eventually be separate FRMSs and Fatigue Safety Action 

Groups for flight operations, maintenance, ground operations, and in-flight services.) The 

thin lines represent information flows. 

Primary responsibility for the FRMS safety assurance processes is assigned to a Quality 

Assurance person or team that is accountable to the Executive Safety Team and: 

• maintains close communication with the Fatigue Safety Action Group; 

• makes recommendations to the Safety Team for Flight Operations, as needed to 

improve the functioning of the FRMS; 

• makes recommendations to the Safety Team for Maintenance, as needed to improve 

the functioning of the FRMS; 

• makes recommendations to the Safety Team for Ground Operations, as needed to 

improve the functioning of the FRMS; 

• makes recommendations to the Safety Team for In-Flight Services, as needed to 

improve the functioning of the FRMS; and 

• monitors changes in the regulatory environment and the operating environment that 

may affect the functioning of the FRMS. 
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Figure 5.4: Example of assignment of responsibility for FRMS safety assurance processes 

in the flight operations department of a large organization 

In a smaller operator, responsibility for the FRMS safety assurance processes might reside 

with an individual rather than a team. This individual may also have a variety of other quality 

assurance responsibilities. A single safety team might be responsible for flight operations, inflight services, ground operations and maintenance. 

5.8 EXAMPLES OF FRMS SAFETY ASSURANCE PROCESSES INTERACTING WITH FRM PROCESSES

Figure 5.5 summarizes interactions between the FRM processes and the FRMS safety 

assurance processes. Together, these two sets of processes form the “engine” of the FRMS. 

Both function in a dynamic way in response to the information and data collected and each is 

responsive to changes in the other. 

The following examples illustrate some FRMS safety assurance processes and describe the 

specific ways in which they interact with the FRM processes. 
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Figure 5.5: Interactions between FRM processes and FRMS safety assurance processes 
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Figure 5.6: FRMS Safety Assurance Processes Example 1 

1. Collect and review information

2. Evaluate overall FRMS 

 performance 

3. Identify emerging fatigue 

 hazards

4. Identify changes affecting 

 FRMS

5. Improve effectiveness of 

 FRMS

Collect and evaluate monthly exceedances of the 13-hour 

scheduled duty limit.

Monthly reviews by the Fatigue Safety Action Group indicate that 

duties exceeding 13 hours have been trending upwards for 3 

months in B-747 operations.

Further analysis shows that most of the trend is due to one hub 

where crews are frequently positioned (dead head) before 

outbound flights or after inbound flights.

Due to a change in marketing strategy, the total number of B-747 

flights in and out of the hub has been steadily increasing for 6 

months.

The Fatigue Safety Action Group recommends an increase in the 

size of the crew base at the hub.

An improvement to the FRM processes is introduced. Monthly 

data are collected and analyzed to monitor the number of flights 

from all crew bases.

In the example in Figure 5.6, as the result of a risk assessment (FRM processes Step 4), the 

Fatigue Safety Action Group sets a duty length of 13 hours as one of its FRMS safety 

performance indicators (SPIs). The target is to have no more than two instances of duties in 

excess of 13 hours per week in B-747 operations. It collects and assesses monthly data on 

scheduled and actual exceedences of the 13-hour duty limit across all its B-747 flights in and 

out of the hub. For 3 consecutive months, there is an increasing trend in exceedences. 
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A short haul example is described in Figure 5.7. Here, the use of captain’s discretion is 

tracked as an FRMS safety performance indicator. (Most State regulations allow for 

maximum flight duty periods to be increased on the day of operation at the discretion of the 

relevant captain.) 

In this example, in the FRMS processes, the Fatigue Safety Action Group has conducted a 

risk assessment (see Table 4.2 d) and decided to set the following thresholds for short haul 

flights: 

• intolerable region - discretion used on at least 25 % of flight duty periods in a two month 

period; 

• tolerable region - discretion used on 10-25 % of flight duty periods in a two month 

period; 

• acceptable region - discretion used on less than 10% of flight duty periods in a two 

month period. 

In addition, delays of more 2 hours must be logged and presented to the Fatigue Safety 

Action Group. 

Data on use of discretion are collected in a log generated by the operator’s crew 

management system. The Fatigue Safety Action Group analyzes this data monthly, to 

ensure that the trips being created by the scheduling software are realistic, given the usual 

operating conditions. The data are sorted by trip (sequence of consecutive flight duty 

periods), distinguishing between regular scheduled trips (that recur for several roster 

periods, e.g., monthly bid lines) and trips that are introduced temporarily to cover variations 

in scheduling or crewmember availability at a particular crew base. Data are also analyzed 

by crewmember rank, category, and qualifications to see, for example, if trips with more 

frequent use of discretion are avoided by more senior crewmembers). 
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Figure 5.7: FRMS Safety Assurance Processes Example 2 

1. Collect and review information

2. Evaluate overall FRMS 

 performance 

3. Identify emerging fatigue 

 hazards

4. Identify changes affecting 

 FRMS

5. Improve effectiveness of 

 FRMS

Use of captain’s discretion recorded in the Operatons’ Log and 

analyzed monthly

An out-and-back daily short-haul trip has had an ‘unacceptable’ level 

of use of captain’s discretion (at least 25% of flights) for 3 

consecutive months, averaging 30 minutes delay beyond the planned 

buffer of 40 minutes for all flights.

Further analysis identify the main causal factors as air traffic control 

en route and ground handling, especially of late passengers to the 

gate.

Schedule Planning and Ground Operations are notified. They had not 

previously identified the issue.

Schedule Planning and Navigation Services file a different route that 

delivers time and fuel savings. Ground Operations management 

negotiates a new Service Level Agreement with the handling agent 

that reduces turnaround times and improves passenger satisfaction 

ratings. Average length of duty periods reduced, use of captain’s 

discretion returns to the acceptable region

Not applicable
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The next example (Figure 5.8) looks at an operator whose FRMS uses scheduled maximum 

values for planning purposes that are well within the established risk-assessed, regulatorapproved, outer boundaries of the FRMS. In this example, on a particular day at a particular 

crew base, the maximum value of scheduled duty time periods defined in the FRMS have 

been exceeded multiple times. 

Every exceedance of the scheduled duty times requires submission of a report to the Fatigue 

Safety Action Group, which is added to the FRMS documentation for regulatory audit. In 

addition, the FRMS safety assurance processes require that the reasons for each 

exceedance are investigated and that, if required, corrective action is taken. In this example, 

the functions of FRMS safety assurance are undertaken by the SMS team as part of their 

broader SMS safety assurance functions. This is to ensure that the management of fatigue 

risks does not result in unintended consequences in overall risk management, that the 

actions taken by the Fatigue Safety Action Group are not self-monitored, and that there is 

appropriate distribution of resources across both the FRMS and the SMS. 

The monthly review of exceedences by the SMS team responsible for FRMS safety 

assurance processes identifies a cluster of exceedences occurring on the same day in the 

same place. They notify the Fatigue Safety Action Group. The Fatigue Safety Action Group 

contacts the line manager responsible for crewing resources on the day and asks him to 

interview the staff on duty on that day. The investigation reveals that there were a series of 

problems that coincided on that particular day, which combined to produce the outcome of 

multiple exceedences of the scheduled duty time limits. It is unlikely that this same 

combination of problems would recur. However, the effectiveness of the FRMS is improved 

by a series of measures that improves the management of staff in the crewing office in times 

of unexpected high workload. 

Monthly analysis of exceedences of the scheduled duty time limits specified in the FRMS 

could consider: 

• the areas of the organization involved in exceedences; 

• causes and extenuating circumstances; and 

• patterns of overdue submission of reports on exceedences. 

The Fatigue Safety Action Group is responsible for developing and implementing any 

recommended mitigations, in consultation with the team responsible for the FRMS safety 

assurance processes. 
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Figure 5.8: FRMS Safety Assurance Processes Example 3 
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Figure 5.9 describes an example that uses another type of FRMS safety performance 

indicator - a code incorporated in the rostering software that indicates when a crewmember 

is approaching the limit for maximum allowable monthly flight hours. If the code is set to 

trigger below the flight hours limit defined in the FRMS policy, then this provides a buffer that 

enables some flexibility and reduces the risk of exceedences. 

Each month, the Fatigue Safety Action Group analyzes how often the code is activated, i.e., 

how often crewmembers are approaching the maximum monthly flight hours, and where this 

is happening. An increasing trend in code indicates increasing workload for flight 

crewmembers, and can be due to an increasing number of flights being scheduled or a 

reduced number of crewmembers available to fly them, or both. Seasonal analyses are also 

undertaken to indicate whether this is a normal cyclical pattern that requires short-term 

remedial action, or a separate upward trend that requires long term remedial action. 

In this example, monthly analyses by the Fatigue Safety Action Group have revealed that 

occurrences of scheduled and actual flight hours triggering the code have increased in July 

compared with June, for Captains at a particular crew base. 

Note: It is possible to incorporate a variety of codes in the rostering software to track when 

different rostering parameters are approaching limits specified in the FRMS. These 

codes can be separated into categories, for example by fleet, crewmember rank and 

crew base, and analyzed in a variety of ways, including: 

• number of times that codes occur for actual versus rostered schedules; 

• analysis of which duty or flight hours limit is most frequently approached, and 

in which part of the operation this is most likely to occur; 

• month-by-month trends in numbers of codes occurring; 

• rolling 13-month trends (recalculated each month for the last 13 months, to 

cover a full cycle of seasonal changes); 

• longer-term trends, for example 3-yearly trends by crewmember rank. 
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Figure 5.9: FRMS Safety Assurance Processes Example 4 

1. Collect and review information

2. Evaluate overall FRMS 

 performance 

3. Identify emerging fatigue 

 hazards

4. Identify changes affecting 

 FRMS

5. Improve effectiveness of 

 FRMS

Code (scheduled and actual) is triggered for Captains at Crew Base A 

more frequently in July than in June.

FRMS Performance Indicator – Code Tracking High 

Monthly Flight Hours

Code relates to the limit of 100 hours of flight time in 28 consecutive 

days. 

Not applicable.

Captains from Crew Base C are added to the roster to help cover 

shortages at Crew Base B.

Captains from Crew Base A that are assigned flights serviced by Crew 

Base B, to help reduce their total flight hours.

In August, the number of times the code is triggered decreases for 

rostered duties for Captains at Crew Base A. Subsequent analyses 

indicate that this change has reduced the use of standby and 

increased roster stability.

Further analysis show that the number of Captains available at Crew 

Base A has been stable for the last 3 months. However, Captains 

from Crew Base A are increasingly being positioned to cover a 

shortage of Captains at Crew Base B. 
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6.0 FRMS PROMOTION PROCESSES 

6.1 INTRODUCTION TO FRMS PROMOTION PROCESSES

This Chapter works through the requirements for FRMS promotion processes that include 

training programs and a communication plan. Figure 6.1 outlines the linkages between the 

FRMS promotion processes and other FRMS components. Along with the FRMS policy and 

documentation, the FRMS promotion processes support the core operational activities of the 

FRMS (FRM processes and FRMS safety assurance processes). 

FRMS training should ensure that all involved personal are trained and competent to 

undertake their responsibilities in the FRMS, and standards for initial and recurrent training 

should be specified in the FRMS documentation. A special feature of FRMS training is that 

key principles of fatigue science - managing sleep and understanding the effects of the 

circadian body clock – are relevant not only to people’s roles in the FRMS but also to their 

lives outside of work, for example in safe motor vehicle driving and in staying healthy. Thus 

FRMS training covers issues that everyone can identify with personally, and this can help 

promote the concept of shared responsibility in an FRMS. 

Like SMS, FRMS relies on effective communication throughout the operator’s organization13. 

On the one hand, there needs to be regular communication about the activities and safety 

performance of the FRMS to all stakeholders. Depending on the structure of the 

organization, this may come from the Fatigue Safety Action Group, the SMS, or from an 

accountable executive responsible for the FRMS communication plan. On the other hand, 

crewmembers and other stakeholders need to communicate promptly and clearly about 

fatigue hazards to the Fatigue Safety Action Group or other relevant management. 

Figure 6.1: Linkages between FRMS promotion processes and other FRMS components 

 

13 ICAO Safety Management Manual (Doc 9859. IATA Introduction to Safety Management Systems (SMS), 2nd Edition, 

Section 5.2. 
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6.2 FRMS TRAINING PROGRAMS

In addition to the above requirements, ICAO Annex 6, Part I, Appendix 8 requires that an 

operator maintain documentation that describes and records FRMS training programs, 

training requirements, and attendance records. It further recommends that regulators have 

competency requirements for FRMS training instructors, who may be part of an operator’s 

internal training department or external contractors. 

6.2.1 Who Needs to be Trained 

For an FRMS to be effective, all personnel who contribute to FRMS safety 

performance need to have appropriate training. This includes crewmembers, crew 

schedulers, dispatchers, operational decision-makers, all members of the Fatigue 

Safety Action Group, and personnel involved in overall operational risk assessment 

and resource allocation. It also includes senior management, in particular the 

executive accountable for the FRMS and senior leadership in any department 

managing operations within the FRMS. 

6.2.2 Curriculum 

The content of training programs should be adapted according to the knowledge 

and skills required for each group to play their part effectively in the FRMS. All 

groups require basic education about the dynamics of sleep loss and recovery, the 

effects of the daily cycle of the circadian body clock, the influence of workload, and 

the ways in which these factors interact with operational demands to produce 

fatigue (see Chapter 2). In addition, it is useful for all groups to have information on 

how to manage their personal fatigue and sleep issues. 

Crewmembers 

The ICAO SMS guidance (Doc 9859) recommends a ‘building-block’ approach to 

training. Applying this approach to FRMS, training for crewmembers could address 

the following areas. 

• An overview of the FRMS structure and how it works in the operator’s 

organization. 

• Their responsibilities and those of the operator, in the FRMS. 

• Causes and consequences of fatigue in the operation(s) in which they work. 

• FRM processes in which they play a vital role, particularly in the use of fatigue 

reporting systems and implementing mitigations. 

• The importance of accurate fatigue data (both subjective and objective). 

Annex 6, Part I, Appendix 8 

4. FRMS promotion processes 

4.1 FRMS promotion processes support the ongoing development of the FRMS, the continuous 

improvement of its overall performance, and attainment of optimum safety levels. The following shall be 

established and implemented by the operator as part of its FRMS: 

a) training programs to ensure competency commensurate with the roles and responsibilities of 

management, flight and cabin crew, and all other involved personnel under the planned FRMS; and 

b) an effective FRMS communication plan that: 

 1) explains FRMS policies, procedures and responsibilities to all relevant stakeholders; and 

 2) describes communication channels used to gather and disseminate FRMS-related information. 
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• How to identify fatigue in themselves and others. 

• Personal strategies that they can use to improve their sleep at home and to 

minimize their own fatigue risk, and that of others, while they are on duty. 

• Basic information on sleep disorders and their treatment, where to seek help if 

needed, and any requirements relating to fitness to fly. 

Crew Scheduling 

FRMS training for personnel involved in crew scheduling could address the 

following areas. 

• An overview of the FRMS structure and how it works in the operator’s 

organization, including the concepts of shared responsibility and an effective 

reporting culture. 

• A robust understanding of how scheduling affects sleep opportunities and can 

disrupt the circadian biological clock cycle, the fatigue risk that this creates, 

and how it can be mitigated through scheduling. 

• Comprehensive training in the use and limitations of any scheduling tools and 

bio-mathematical models or other algorithms that may be used to predict the 

levels of crewmember fatigue across schedules and rosters. 

• Their role in the FRMS in relation to fatigue hazard identification and risk 

assessment. 

• Processes and procedures for assessing the potential fatigue impact of 

planned scheduling changes, and for ensuring that the Fatigue Safety Action 

Group is engaged early in the planning of changes with significant potential to 

increase fatigue risk. 

• Processes and procedures for implementing scheduling changes 

recommended by the Fatigue Safety Action Group. 

• How to identify fatigue in themselves and others. 

• Personal strategies that they can use to improve their sleep at home and to 

minimize their own fatigue risk, and that of others, while they are at work. 

• Basic information on sleep disorders and their treatment, and where to seek 

help if needed. 

Fatigue Safety Action Group 

FRMS training for members of the Fatigue Safety Action Group, and for others with 

responsibility for safety decision-making that affects FRMS performance, could 

address (at least) the following areas. 

• A full understanding of all FRMS components and elements (policy and 

documentation; processes for hazard identification, risk assessment, 

mitigation, and monitoring; safety assurance processes for monitoring FRMS 

performance, managing change, and for continuous improvement of the 

FRMS; and FRMS promotion processes, including training and 

communication). 

• The responsibilities and accountabilities of different stakeholders in the 

FRMS. 

• Linkages between the FRMS and other parts of the operator’s overall safety 

management system. 

• Linkages between the FRMs and other parts of the organization, for example 

the scheduling department, flight operations, medical department, etc. 
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• Regulatory requirements for the FRMS. 

• How to identify fatigue in themselves and others. 

• Personal strategies that they can use to improve their sleep at home and to 

minimize their own fatigue risk, and that of others, while they are at work. 

• Basic information on sleep disorders and their treatment, and where to seek 

help if needed. 

Senior Management 

FRMS training for senior management could address the following areas. 

• An overall understanding of crewmember fatigue and the safety risk that it 

represents to the organization. 

• An overview of the FRMS structure and how it works, including the concepts 

of shared responsibility and an effective reporting culture, and the role of the 

Fatigue Safety Action Group. 

• The responsibilities and accountabilities of different stakeholders in the 

FRMS, including themselves. 

• An overview of the types of fatigue mitigation strategies being used by the 

organization. 

• FRMS safety assurance metrics used by the organization. 

• Linkages between the FRMS and other parts of the operator’s safety 

management system. 

• Linkages between the FRMS and other parts of the organization, for example 

the scheduling department, flight operations, medical department, etc. 

• Regulatory requirements for the FRMS. 

• How to identify fatigue in themselves and others. 

• Personal strategies that they can use to improve their sleep at home and to 

minimize their own fatigue risk, and that of others, while they are at work. 

• Basic information on sleep disorders and their treatment, and where to seek 

help if needed. 

Examples of training materials developed by the NASA Fatigue Countermeasures 

Program for flight crew in different types of operations are freely available on the 

internet. 14

• The original generic training package ‘Crew Factors in Flight Operations X: 

Alertness Management in Flight Operations Education Module’ is available at: 

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020078410_20021265

47.pdf

• The training package ‘Crew Factors in Flight Operations XIV: Alertness 

Management in Regional Flight Operations Education Module’ is available at: 

http://human-factors.arc.nasa.gov/zteam/PDF_pubs/REGETM_XIV.pdf

• The training package ‘Crew Factors in Flight Operations XV: Alertness 

Management in General Aviation Education Module’ is available at: 

http://humanfactors.arc.nasa.gov/publications/B_Flight_Ops_XV_GAETM1.pd

f

 

14 Web addresses accurate as of August 2, 2010 
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These training packages draw on fatigue-related safety data and scientific 

research. Each package includes a slide presentation with explanatory text. They 

are designed to be used as a personal resource by crewmembers, and/or as a live 

presentation that lasts at least an hour. In addition, the Regional and General 

Aviation Modules include summaries from a number of NASA studies and safety 

reports. It should be noted that these materials date from 2001-2002 and need to 

be updated to include more recent safety and scientific data, and to reflect current 

operating conditions. Nevertheless, they provide useful examples of the type and 

level of information that can be used in initial FRMS training, particularly for flight 

crew. They are useful examples, but each operator will need to look at how 

relevant the training materials are for their particular operational needs. 

Table 6.1 provides some examples of personal fatigue mitigation strategies that 

might be covered in FRMS training for flight crew. 

Table 6.1: Examples of Fatigue Hazards and Personal Mitigation Strategies (Not 

an Exhaustive List) 

Fatigue Hazard Personal Mitigation Strategies

Sleep at home 

disturbed by new baby 

• Move to a quiet part of the house for final sleep 

before departure. 

• Maximize sleep in 24 hours before departure. 

• Controlled flight deck napping, maximize sleep 

during in-flight rest periods (if available). 

• Strategic use of caffeine in flight 

In-flight sleepiness on 

non-augmented flights 

• Maximize sleep in 24 hours before departure. 

• Controlled flight deck napping, strategic use of 

caffeine in flight. 

Difficulty sleeping in 

onboard crew rest 

facilities 

• Maximize sleep in 24 hours before departure. 

• Use eye mask, ear plugs, arrange a suitable wakeup 

call. 

• Avoid caffeine for 3-4 hours before trying to sleep. 

• Strategic use of caffeine after in-flight rest period. 

Difficulty sleeping in 

noisy, poorly-curtained 

rooms in layover hotel 

• Submit a fatigue report to the Fatigue Safety Action 

Group. 

• Use eye mask, ear plugs, arrange a suitable wakeup 

call. 

• Avoid caffeine for 3-4 hours before trying to sleep. 

Non-restorative sleep • See a sleep disorders specialist. 

• Comply fully with recommended treatment 
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Table 6.1 continued 

Fatigue Hazard Personal Mitigation Strategies

Unpredictable call-outs • Ensure that sleep environment is dark and quiet, and 

use sleep hygiene measures to maximize sleep 

quality. 

• Maximise recovery sleep on off-duty days. 

• When feeling sleepy while waiting for call-out, 

attempt sleep (prioritise sleep over other activities). 

• Controlled flight deck napping, maximize sleep 

during in-flight rest periods (if available). 

• Strategic use of caffeine in flight 

A specific city pairing 

results in landing when 

extremely fatigued. 

• Submit a fatigue report to the Fatigue Safety Action 

Group. 

• Controlled flight deck napping. 

• Maximize sleep during in-flight rest periods (if 

available). 

• Strategic use of caffeine in flight. 

Extended commute 

prior to scheduled flight 

duty period. 

• Arrive at duty location with sufficient time to allow 

adequate sleep, ensuring fitness for duty. 

6.2.3 FRMS Training Formats and Frequency 

There are a variety of ways in which FRMS training can be delivered, each of 

which has strengths and limitations. Live training sessions with a trained instructor 

have the advantage that crewmembers can ask questions about their specific 

issues or concerns, and can learn from each other’s experiences. Face-to-face 

contact with different stakeholders in the FRMS can facilitate building the safety 

culture. However, live training requires coordinating a time and place that groups of 

participants can attend, and involves time getting to and from the venue, in addition 

to the time required for the actual training session. 

Web-based learning or distributed training (for example, using DVDs) allows 

greater flexibility in the time and place that training occurs. Individual participation 

allows participants to proceed at their own pace through the training materials. In 

web-based learning, sessions can be networked so that multiple participants can 

join in with a tutor on-line. Material can also be made interactive (a task has to be 

completed, for example a short quiz answered, before the participant can move on 

to the next part of the training). Participants and tutors can interact via designated 

‘chat rooms’. Web-based learning programs can also direct participants to explore 

a variety of other resources available on the internet. On the other hand, it is 

harder to eliminate ‘cheating’ when learning assessments are completed on-line 

than when they are completed in a classroom. This may be important for training 

evaluation (see below). 
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Providing different materials and formats for recurrent training can help to maintain 

interest. For example, recent fatigue reports or Fatigue Safety Action Group 

interventions can be used as case studies to illustrate and revise concepts covered 

in the initial training material. Recurrent training can also cover changes to the 

operations or the FRMS, and scientific and regulatory updates. The frequency and 

nature of recurrent training needs to be decided by the Fatigue Safety Action 

Group, in consultation with professional trainers (internal or external to the 

operator) as needed. Many regulators may also prescribe requirements on the 

frequency of FRMS training. 

6.2.4 FRMS Training Evaluation 

The effectiveness of FRM training and education programs should be periodically 

evaluated. Examples of evaluation tools can include the following. 

• To evaluate immediate knowledge transfer from a training session, 

participants can be given a short quiz assessing fatigue knowledge, to be 

completed before and after the training session (for an example, see the text 

box below). 

• To evaluate the amount of knowledge retained, crewmembers’ use of 

suggested countermeasure strategies, and perceived usefulness of training, a 

survey can be conducted at a fixed time after training (for example, 6 months). 

• Findings from the quiz and surveys can be used to: 

a) revise the content of the training package, to improve the training on 

topics which a significant proportion of crewmembers have not fully 

understood; 

b) provide feedback to trainers on areas where they may need to change or 

improve their teaching approaches; and 

c) identify areas that need to be reviewed or added in recurrent training. 
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6.2.5 FRMS Training Documentation 

ICAO Annex 6, Part I, Appendix 8 requires that an operator keep documentation 

that describes and records FRMS training programs, training requirements, and 

attendance records. 

6.2.6 FRMS Communications Plan 

ICAO Annex 6, Part I, Appendix 8 requires an operator to have an FRMS 

communication plan that: 

1. explains FRMS policies, procedures and responsibilities to all stakeholders; 

and 

2. describes communication channels used to gather and disseminate FRMSrelated information. 

The FRMS training programs are clearly an important part of the communication 

plan. However, training generally occurs at fairly long intervals (for example 

annually). In addition, there needs to be ongoing communication to stakeholders 

about the activities and safety performance of the FRMS, to keep fatigue ‘on the 

radar’ and encourage the continuing commitment of all stakeholders. A variety of 

types of communication can be used, including electronic media (websites, on-line 

forums, e-mail), newsletters, bulletins, seminars, periodic poster campaigns in 

strategic locations, etc. 

QUIZ (for use before and after initial training) 

Are these ideas true or false? Please tick one box for each question. 

1. Sleep is a time when your brain switches off.  True  False 

2. Dreaming sleep is better for you than non-dreaming sleep.  True  False 

3. In the end, the only way to get rid of sleepiness is to get some sleep.  True  False 

4. You can always beat sleepiness, if you try hard enough.  True  False 

5. As you get sleepier, your reaction time slows down.  True  False 

6. Napping is a sign of laziness.  True  False 

7. The circadian body clock adapts easily to sleeping during the day.  True  False 

8. There are two times of day when your circadian body clock makes you feel most 

sleepy, around 3-5 am and 3-5 pm. 

 True  False 

9. Having a regular routine at bedtime can help you to fall asleep more easily.  True  False 

10. A dark, quiet room helps you sleep better.  True  False 

11. If you drink too much coffee and can’t sleep, you should drink some alcohol to help 

you relax. 

 True  False 

12. Even if you are not sleepy, you should start each flight with a cup of coffee, to fight 

fatigue. 

 True  False 

13. You are on the flight deck and you feel incredibly sleepy. The best thing to do is not to 

tell anyone, and to try extra hard to stay focused. 

 True  False 

14. Fatigue would not be a problem if the schedules were properly designed.  True  False 
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Communications about the activities and safety performance of the FRMS (from 

the Fatigue Safety Action Group or other designated management) need to be 

clear, timely and credible, i.e., consistent with the facts and with previous 

statements. The information provided also needs to be tailored to the needs and 

roles of different stakeholder groups, so that people are not swamped by large 

quantities of information that has little relevance to them. 

Communications from crewmembers are vital for fatigue hazard identification, for 

feedback on the effectiveness of controls and mitigations, and in providing 

information for FRMS safety performance indicators (for example, by participating 

in surveys and fatigue monitoring studies). For these communications to be open 

and honest, all FRMS stakeholders need to have a clear understanding of the 

policies governing data confidentiality and the ethical use of information provided 

by crewmembers. There also needs to be clarity about the thresholds that separate 

non-culpable fatigue-related safety events from deliberate violations that could 

attract penalties. 

Timely feedback to crewmembers who submit fatigue reports is vital. Feedback 

does not require completion of a full investigation. Every crewmember should 

receive a timely response to their report with some indication of the planned followup activity. For example - “To Capt Smyth; thank you for your fatigue report 

yesterday regarding flight 123 from AA to ZZ. This report has been forwarded to 

the Fatigue Safety Action Group, which is currently investigating an adverse trend 

in fatigue reports associated with this trip and is evaluating a number of potential 

mitigation strategies”. 

The communication plan needs to be described in the FRMS documentation and 

assessed periodically as part of FRMS safety assurance processes 
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7.0 FRMS IMPLEMENTATION 

7.1 INTRODUCTION TO FRMS IMPLEMENTATION

There is no ‘off-the-shelf’ version of an FRMS that will suit all operators. Each operator 

needs to develop an FRMS that is appropriate to its organisation and operations and the 

nature and level of the fatigue risk(s). 

The implementation of an FRMS can be done in stages, as is recommended for SMS. 15 The 

idea is to have a series of manageable steps so that resources and workload can be 

allocated over a period of time, rather than having to have everything available before 

implementation can begin. Having a staged approach is also a way to manage the 

complexity of the task, focusing on one step at a time. Figure 7.1 summarises a staged 

approach to FRMS implementation, based on the SMS model. 

Figure 7.1: Stage approach to FRMS implementation 

Once an operator has decided to implement an FRMS, and has reviewed the regulators 

requirements, they should notify the regulator that they wish to proceed. Full implementation 

of an FRMS involves four phases, each of which shoud to be reviewed by the regulator 

before the next phase begins. At the end of the fourth phase, the operator can seek 

regulatory approval for the full FRMS. 

 

15 ICAO Safety Management Manual (Doc 9859) Chapter 10. IATA Introduction to Safety Management Systems 

(SMS), 2nd Edition, Section 8. 
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7.2 PHASE I: PLANNING

The objective of Phase I is to arrive at an overall plan of how the FRMS will function, how it 

will be integrated with other parts of the operator’s organization, who will be accountable for 

the FRMS, and who will be accountable for making sure that FRMS implementation is 

successfully completed. 

Gap Analysis and Developing an Implementation Plan 

Many elements needed for an FRMS may already be in place in an operator’s organization. 

One of the first steps in FRMS implementation is therefore to undertake a gap analysis to: 

• identify elements of the FRMS that are already available in existing systems and 

process; and 

• identify existing systems and process that could be modified to meet the needs of 

FRMS (to minimize ‘re-inventing the wheel’); and 

• identify where new systems and processes need to be developed for the FRMS. 

For example, an operator may already have a confidential safety reporting system as part of 

its SMS. Existing report forms may (or may not) need to be modified to include the 

information needed to analyze the role of fatigue in safety events. Additional training may (or 

may not) be needed for the staff responsible for analyzing safety data, to ensure that they 

know how to analyze for the role of fatigue in events. A procedure will need to be added for 

information on fatigue-related events to be communicated on a regular basis to the Fatigue 

Safety Action Group. Fatigue reports may also be used as an FRMS safety performance 

indicator. In this case, a procedure would need to be added for this information to be 

evaluated regularly as part of the FRMS safety assurance processes. 

Data on scheduled and actual flight and duty times are required to be collected under the 

fatigue management regulations. An operator that is moving some of its operations into an 

FRMS could add a variable to the existing flight and duty time databases to identify the 

operations covered by the FRMS, so that this information can be analyzed separately as 

required for the FRMS (Annex 6, Part I, Appendix 8). Procedures will need to be added for 

this information to be communicated to the Fatigue Safety Action Group and recorded as 

required in the FRMS documentation. 

Rostering-related data may already be available for FRMS performance indicators, for 

example monthly significant exceedences on duty limits, use of captain’s discretion, or use of 

extended duties. A procedure will need to be added for this information to be evaluated 

regularly as part of the FRMS safety assurance processes. 

It may be efficient to schedule FRMS training to coincide with other training activities that 

already bring the target groups together. 

The ICAO SMS Guidance (SMM Chapter 7, Appendix 2) provides a detailed checklist for a 

gap analysis that works systematically through all the elements of an SMS. This could be 

modified to work though the elements of an FRMS as identified in Figure 3.1 (Chapter Three, 

this manual). 

The results of the gap analysis are used to inform the development of the FRMS 

implementation plan - a road map describing how the implementation will proceed, including 

timelines. 
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By the end of Phase I, the following steps need to be accomplished. 

• Gap analysis. 

• FRMS Policy Statement signed by the accountable executive. Developing the policy at 

the beginning of the FRMS implementation process will assist in defining the scope of 

the FRMS. 

• FRMS implementation plan. 

• FRMS documentation plan. This can be expected to evolve as the FRMS becomes 

operational. 

• FRMS communication plan. This can be expected to evolve as the FRMS becomes 

operational. 

• Allocation of financial and human resources. The Accountable Executive for the FRMS 

needs to have the authority and control to ensure that this happens. 16 

• Fatigue Safety Action Group (or equivalent) established. The stage at which the Fatigue 

Safety Action Group is established will vary, according to the size and complexity of the 

organization and the FRMS, and whether there are suitably qualified people in other 

parts of the organization who are available to begin the Phase I activities. 

7.3 PHASE II: IMPLEMENT REACTIVE FRM PROCESSES

Phase II implements the (first version) of the FRM processes, based on reactive hazard 

identification (Chapter Four). It does this by gathering and analyzing existing sources of 

information and data that are relevant to the operations covered by the FRMS. Types of 

information that may be available include confidential safety reports, accident reports and 

incident investigations, audits, and historical rostering data (for example, data on scheduled 

and actual flight and duty times, exceedences, etc.). In effect, Phase II activities consolidate 

existing fatigue risk management processes and procedures in the organization, and 

introduce controls and mitigations to manage identified deficiencies in the existing system. 

By the end of Phase II, the following steps need to be accomplished. 

• FRM processes based on reactive hazard identification are operational, including risk 

assessment and the development, implementation, and monitoring of appropriate 

controls and mitigations. 

• FRMS documentation processes are established to support the current version of the 

FRMS. 

• FRMS training activities are established to support the current version of the FRMS. 

(Stakeholders need training to ensure that they are competent to undertake their 

responsibilities in the FRMS as the implementation plan rolls out). 

• FRMS communication processes are established to support the current version of the 

FRMS. 

• The operator is ready to undertake coordinated safety analyses of this first version of 

the FRMS (ICAO SMM 10.4). 

 

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Phase III adds proactive and predictive fatigue hazard identification processes (discussed in 

Chapter Four) into the FRMS processes established in Phase II. 

By the end of Phase III, the following steps need to be accomplished. 

• FRM processes based on reactive, proactive, and predictive hazard identification are 

operational, including risk assessment and the development, implementation, and 

monitoring of appropriate controls and mitigations. 

• FRMS documentation processes are established to support the current version of the 

FRMS. 

• FRMS training activities are established to support the current version of the FRMS. (A 

single program to the level required for the full FRMS implementation may be more 

efficient than part-training at each Phase of the implementation.) 

• FRMS communication processes are established to support the current version of the 

FRMS. 

• The operator is ready to undertake coordinated safety analyses of this version of the 

FRMS, similar to the process used when implementing SMS (ICAO SMM 10.4). 

7.5 PHASE IV: IMPLEMENT FRMS SAFETY ASSURANCE PROCESSES

Phase IV activates the FRMS safety assurance processes (Chapter Five of this manual). By 

the end of Phase IV, the following steps need to be accomplished. 

• Roles and responsibilities for assuring the safety performance of the FRMS are 

established. 

• The necessary authorities and communication channels are active. 

• FRMS safety performance indicators have been developed and agreed on. 

• The procedures and processes for periodic evaluation of the safety performance 

indicators are established. 

• Appropriate feedback is established between the FRM processes and the FRMS safety 

assurance processes. 

• FRMS documentation processes are fully implemented. 

• FRMS training processes are fully implemented. 

• FRMS communication processes are fully implemented. 

In other words, by the end of Phase IV, the FRMS should be fully functional and integrated 

with the operator’s SMS and other parts of the organization as appropriate. It should be 

continuously improving and able to respond to changes in the organization and the operating 

environment. Having an FRMS has been described by one operator as making his 

organization ‘nimble’, in the sense of being able to respond quickly when market 

opportunities arise (for example new routes that become viable when aircraft capabilities 

change). 

Regulatory approval for the full FRMS is sought at the end of Phase IV. 
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7.6 OPERATIONAL EXAMPLE OF STAGED FRMS IMPLEMENTATION

Operator A is a major airline that flies primarily long range, trans-oceanic flights with multinational crews. It has been flying for 20 years with an excellent safety record. Operator A is 

interested in starting an FRMS for both of its long range fleets. The CEO decides to 

implement FRMS for the entire operation to enhance safety and efficiency. 

This example works through the steps that Operator A could follow to implement a fully 

operational FRMS. It assumes that management at Operator A are familiar with information 

in this Implementation Guide and are ready to start implementation. 

Phase I 

1. Responsibility for FRMS implementation assigned to a designated FRMS manager. 

2. FRMS manager assembles an implementation team, and organizes training for the 

team on FRMS basics and fatigue science. 

3. Accountable Executive for the FRMS allocates resources and authority to support 

FRMS development. 

4. FRMS manager identifies internal stakeholders (department representatives). 

5. FRMS policy statement is drafted. 

6. Gap analysis undertaken by FRMS manager and implementation team. 

7. FRMS documentation plan developed and first draft established. 

8. FRMS communication plan developed and first draft established. 

9. Implementation plan developed, with initial timeline. 

10. Fatigue Safety Action Group established with required stakeholder membership and 

meets regularly with the implementation team (if different employees) to discuss 

progress. 

Phase II 

11. Fatigue Safety Action Group works through the FRM process diagram (Chapter 4), 

using existing information and data for reactive fatigue hazard identification. 

a) Step 1 - decide whether domestic, international long haul and ULR operations 

require different FRM processes. Carry out the following steps for each set of FRM 

processes. 

b) Step 2 –collect and analyze available data and information (for example 

confidential safety reports, accident reports and incident investigations, audits, and 

historical rostering data). 

c) Step 3 – Identify fatigue hazards(s) 

d) Step 4 – establish risk assessment processes and procedures. Clarify linkages to 

SMS risk assessment and processes for prioritization of risks to be mitigated. (In 

this large airline example, the FRMS policy statement indicates that the Fatigue 

Safety Action Group is responsible for prioritizing fatigue risks, and for developing, 

implementing, and monitoring fatigue controls and mitigations. It is required to 

provide monthly reports of these activities to the SMS Review Board, with the 

intent that this report will become part of the FRMS safety assurance process in 

the overall FRMS.) 

e) Step 5 – select and implement controls and mitigations. Set safety performance 

indicators. 

f) Step 6 – set up processes for monitoring the effectiveness of controls and 

mitigations 
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12. Perform training to ensure that stakeholders are competent to undertake their roles and 

responsibilities in the FRMS. In this example, it is decided to undertake training to 

support the full FRMS. Communication channels are set up to provide training updates 

and reminders when Phases III and IV of the FRMS implementation become active. 

13. FRMS communication channels established. 

14. Fatigue Safety Action Group provides a coordinated safety analysis of the existing 

FRMS to the SMS Review Board. (The SMS Review Board is responsible for the FRMS 

safety assurance functions, in this example). 

Phase III 

15. For each set of FRMS processes established in Phase II, the Fatigue Safety Action 

Group identifies appropriate tools for proactive and predictive fatigue hazard 

identification. 

a) Proactive fatigue identification tools are used for assessing routine and complex 

hazards. 

16. Proactive and predictive fatigue hazard identification are integrated in to the FRM 

processes established in Phase II. 

17. All stakeholders have received suitable training and are competent to undertake their 

roles and responsibilities in the FRMS. 

18. FRMS communication channels are operational. 

19. Fatigue Safety Action Group provides a coordinated safety analysis of the existing 

FRMS to the SMS Review Board. 

Phase IV 

20. FRMS safety performance indicators are decided collaboratively by the Fatigue Safety 

Action Group and the SMS Review Board and approved by the Accountable Executive 

for the FRMS. 

a) Decide which information that will be analyzed for trends (e.g., fatigue reporting 

rates between similar city pairs, operations, or fleets) 

b) Develop criteria for comparing performance with safety objectives (for example, is 

the overall risk level increasing, is the number of higher risk events increasing, are 

safety objective in the FRMS policy being achieved, are regulatory requirements 

being met). 

c) Decide how emerging fatigue hazards are identified. For example, set triggers to 

identify when action is needed (at what level do adverse trends in performance 

indicators trigger an investigation of the causes of the trend). 

21. Processes are established for identifying changes that could impact the FRMS. 

22. Processes are established for evaluating how well Fatigue Safety Action Group 

recommendations are implemented in other parts of the organization, for example in 

scheduling and flight operations. 
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23. The following safety assurance processes are established. 

a) Monthly reporting by the Fatigue Safety Action Group to the SMS Review Board. 

To include updates on fatigue hazards identified and on the status of agreed safety 

performance indicators. 

b) SMS Review Board able call for special reports from the Fatigue Safety Action 

Group, for example after significant operational changes such as a newly 

established route. 

c) Quarterly review of trends in confidential crew reports relating to fatigue, to be 

undertaken by the Fatigue Safety Action Group and reported to the SMS Review 

Board. 

d) Quarterly review of exceedences of flight and duty time limits specified in the 

FRMS Policy, to be undertaken by the Fatigue Safety Action Group and reported to 

the SMS Review Board. 

e) Quarterly review of trends in FRMS safety performance indicators identified in the 

FRMS policy, to be undertaken by the Fatigue Safety Action Group and reported to 

the SMS Review Board. 

f) Annual review of fatigue hazard identification and mitigation activities of the 

Fatigue Safety Action Group by an independent FRMS Scientific Advisory Group. 

g) Internal audit of the FRMS by a team selected by the SMS Review Board. 

h) Annual report of the Fatigue Safety Action Group to the SMS Review Board and 

the Accountable Executive for the FRMS, to include the recommendations of the 

independent FRMS Scientific Advisory Group, findings of audits, and actions 

taken in response to them. 

24. First quarterly audit of FRMS safety performance by the team selected by the SMS 

Review Board. If audits are satisfactory for one year, internal audit will revert to every 6 

months. 

25. FRMS documentation fully implemented. 

26. FRMS training fully implemented. 

27. FRMS communications fully implemented. 
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APPENDIX A

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 APPENDIX A: GLOSSARY 

* denotes an ICAO definition. 

Actigraph (or Actiwatch). 

A wristwatch-like device containing an accelerometer to detect movement. Activity counts are 

recorded per unit time, for example every minute. The patterns of movement can be analyzed using 

purpose-built software to estimate when the wearer of the actiwatch was asleep, and to provide 

some indication of how restless a sleep period was (i.e., sleep quality). Actigraphs are designed to 

record continuously for several weeks so they are valuable tools for monitoring sleep patterns, for 

example before, during, and after a trip 

Actigraphy. 

Use of actiwatches to monitor sleep patterns. For actigraphy to be a reliable measure of sleep, the 

computer algorithm that estimates sleep from activity counts must have been validated against 

polysomnography, which is the gold standard technology for measuring sleep duration and quality. 

The main weakness of actigraphy is that an actigraph cannot differentiate between sleep and still 

wakefulness (since it measures movement). 

Afternoon Nap Window 

A time of increased sleepiness in the middle of the afternoon. The precise timing varies, but for 

most people it is usually around 15:00-17:00. This is a good time to try to nap. On the other hand, 

it is also a time when it is more difficult to stay awake, so unintentional micro-sleeps are more likely, 

especially if recent sleep has been restricted 

Augmented Flight Crew 

A flight crew that comprises more than the minimum number required to operate the aeroplane so 

that each crewmember can leave his or her assigned post to obtain in-flight rest and be replaced by 

another appropriately qualified crewmember. 

Augmented Long Range Operations 

Flights where the flight duty period is extended through the use of augmented crews, allowing 

crewmembers the opportunity for in-flight rest. 

Bio-mathematical Model 

A computer programme designed to predict crewmember fatigue levels, based on scientific 

understanding of the factors contributing to fatigue. All bio-mathematical models have limitations 

that need to be understood for their appropriate use in an FRMS. An optional tool (not a 

requirement) for predictive fatigue hazard identification (ICAO Annex 6, Part 1, Appendix 8, Section 

2.1.) 

Chronic fatigue 

In fatigue risk management, chronic fatigue refers to the sleepiness and performance impairment 

that accumulate when sleep is restricted day after day. These effects can be reversed by obtaining 

adequate recovery sleep (also see cumulative sleep debt). 
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Chronic Fatigue Syndrome 

Medical condition for which the diagnosis requires a person must meet two criteria: 

1. Have severe chronic fatigue for at least 6 months or longer that is not relieved by rest and not 

due to medical or psychiatric conditions associated with fatigue as excluded by clinical 

diagnosis; and 

2. Concurrently have four or more of the following symptoms: self-reported impairment in shortterm memory or concentration severe enough to cause substantial reduction in previous levels 

of occupational, educational, social, or personal activities; sore throat that is frequent or 

recurring; tender lymph nodes in the neck or armpits; muscle pain; multi-joint pain without 

swelling or redness; headaches of a new type, pattern, or severity; unrefreshing sleep; and 

post-exertional malaise (extreme, prolonged exhaustion and sickness following physical or 

mental activity) lasting more than 24 hours. 

 The fatigue and impaired memory or concentration must have impaired normal daily activities, 

along with other symptoms that must have persisted or recurred during 6 or more consecutive 

months of illness and must not have predated the fatigue. 

http://www.cdc.gov/cfs/general/case_definition/index.html

Circadian Body Clock 

A neural pacemaker in the brain that monitors the day/night cycle (via a special light input pathway 

from the eyes) and determines our preference for sleeping at night. Shift work is problematic 

because it requires a shift in the sleep/wake pattern that is resisted by the circadian body clock, 

which remains ‘locked on’ to the day/night cycle. Jet lag is problematic because it involves a 

sudden shift in the day/night cycle to which the circadian body clock will eventually adapt, given 

enough time in the new time zone. 

Controls 

System-level defensive strategies designed to minimize fatigue risk on an ongoing basis. Examples 

include: scheduling rules, monitoring staffing levels at crew bases, selection of appropriate in-flight 

crew rest facilities, and protocols for in-flight rest and controlled rest on the flight deck. 

Controlled flight deck napping 

An effective mitigation strategy to be used as needed in response to fatigue experienced during 

flight operations. Recommended procedures for controlled flight deck napping can be found in 

Appendix C. It should not be used as a scheduling tool, i.e., as a planned strategy to enable 

extended duty periods 

Countermeasures 

Personal mitigation strategies that crewmembers can use to reduce their own fatigue risk. 

Sometimes divided into strategic countermeasures (for use at home and on layovers, for example 

good sleep habits, napping before night duty), and operational countermeasures for use in flight, for 

example controlled rest on the flight deck. 

*Crewmember 

A person assigned by an Operator to duty on an aircraft during a flight duty period 

Crew Pairing 

A set of scheduled flights on which a crewmember is rostered for one or more days. 
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Cumulative sleep debt 

Sleep loss accumulated when sleep is insufficient for multiple nights (or 24-hr days) in a row. As 

cumulative sleep debt builds up, performance impairment and objective sleepiness increase 

progressively, and people tend to become less reliable at assessing their own level of impairment 

*Duty 

Any task that crew members are required by the Operator to perform, including, for example, flight 

duty, administrative work, training, positioning and standby when it is likely to induce fatigue 

*Duty Period 

A period which starts when a flight or cabin crew member is required by an Operator to report for or 

to commence a duty and ends when that person is free from all duties. 

Evening Type 

A person whose natural sleep time is later than average as a result of the characteristics of their 

circadian biological clock. There is also a developmental trend to become more evening-type 

across puberty, which reverses for most people in adulthood. 

Evening Wake Maintenance Zone 

A period of several hours in the circadian body clock cycle, just before usual bedtime, when it is 

very difficult to fall asleep. Consequently, going to bed extra early usually results in taking a longer 

time to fall asleep, rather than getting extra sleep. Can cause restricted sleep and increased fatigue 

risk with early duty start times. 

*Fatigue 

A physiological state of reduced mental or physical performance capability resulting from sleep loss 

or extended wakefulness, circadian phase, or workload (mental and/or physical activity) that can 

impair a crew member’s alertness and ability to safely operate an aircraft or perform safety related 

duties. 

FRMS Training 

Competency-based training programs designed to ensure that all stakeholders are competent to 

undertake their responsibilities in the FRMS. 

Fatigue Safety Action Group (FSAG) 

A group comprised of representatives of all stakeholder groups (management, scheduling, crew 

representatives) together with specialist scientific, data analysis, and medical expertise as 

required), that is responsible for coordinating all fatigue management activities in the organisation. 

Fatigue Risk Management 

The management of fatigue in a manner appropriate to the level of risk exposure and the nature of 

the operation, in order to minimise the adverse effects of fatigue on the safety of operations. 

Fatigue Risk Management System Policy 

A required component of an FRMS (ICAO Annex 6, Part 1, Appendix 8, Section 1.1). THE FRMS 

Policy must: identify the elements of the FRMS and its scope; reflect the shared responsibility of all 

stakeholders in the FRMS; state the safety objectives of the FRMS; be signed by the accountable 

executive of the organisation; be communicated throughout the organisation; declares 

management commitment to effective safety reporting, to providing adequate resourcing for the 

FRMS, and to continuous improvement of the FRMS; identify clear lines of accountability for the 

functioning of the FRMS; and require periodic reviews of the FRMS. 
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*Fatigue Risk Management System (FRMS). 

A data-driven means of continuously monitoring and managing fatigue-related safety risks, based 

upon scientific principles and knowledge as well as operational experience that aims to ensure 

relevant personnel are performing at adequate levels of alertness. 

Fatigue Safety Assurance 

FRMS safety assurance processes monitor the entire FRMS to check that it is functioning as 

intended and meeting the safety objectives in the FRMS policy and regulatory requirements. FRMS 

safety assurance processes also identify operational and organizational changes that could 

potentially affect the FRMS, and identify areas where the safety performance of the FRMS could be 

improved (continuous improvement). 

*Flight data analysis (FDA) 

A process of analyzing recorded flight data in order to improve the safety of operations. 

*Flight duty period 

A period which commences when a crew member is required to report for duty that includes a flight 

or a series of flights and which finishes when the aeroplane finally comes to rest and the engines 

are shut down at the end of the last flight on which he/she is a crew member. 

*Flight time – aeroplanes 

The total time from the moment an aeroplane first moves for the purpose of taking off until the 

moment it finally comes to rest at the end of the flight. 

Homeostatic Sleep Pressure 

See Sleep Homeostatic Process 

Internal Alarm Clock 

A time in the circadian body clock cycle when there is a very strong drive for waking and it is 

difficult to fall asleep or stay asleep. Occurs about 6 hours after the Window of Circadian Low in 

the late morning to early afternoon and can cause restricted sleep and increased fatigue risk after 

night duty. 

Jet Lag 

Desynchronization between the circadian body clock and the day/night cycle caused by 

transmeridian flight (experienced as a sudden shift in the day/night cycle). Also results in internal 

desynchronization between rhythms in different body functions. Common symptoms include 

wanting to eat and sleep at times that are out of step with the local routine, problems with digestion, 

degraded performance on mental and physical tasks, and mood changes. Resolves when sufficient 

time is spent in the new time zone for the circadian body clock to become fully adapted to local time 

Micro-sleep 

A short period of time (seconds) when the brain disengages from the environment (it stops 

processing visual information and sounds) and slips uncontrollably into light non-REM sleep. Microsleeps are a sign of extreme physiological sleepiness. 

Mitigations 

System-level interventions designed to reduce a specific identified fatigue risk. Examples include: 

increasing the number of crewmembers at a base, use of reserve crew, educating crewmembers 

on how to obtain optimal in-flight sleep, Captain’s discretion to re-organize in-flight rest 

arrangements on the day of flight in response to crewmembers’ fatigue levels and operational 

conditions, etc. 
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Morning Type 

A person whose natural sleep time is earlier than average as a result of the characteristics of their 

circadian biological clock. There is also a developmental trend to become more morning-type 

across adulthood. 

Nap 

A brief period of sleep, usually defined as less than half of a full night time sleep period. Naps as 

short as 5 minutes have been shown to provide (temporary) relief from the cumulative effects of 

sleep loss – also see controlled flight deck napping 

Non-Rapid Eye Movement Sleep (Non-REM Sleep) 

A type of sleep associated with gradual slowing of electrical activity in the brain (seen as brain 

waves measured by electrodes stuck to the scalp, known as EEG). As the brain waves slow down 

in non-REM sleep, they also increase in amplitude, with the activity of large groups of brain cells 

(neurons) becoming synchronized. Non-REM sleep is usually divided into 4 stages, based on the 

characteristics of the brainwaves. Stages 1 and 2 represent lighter sleep. Stages 3 and 4 represent 

deeper sleep and are also known as slow-wave sleep. 

Non-REM/REM Cycle 

Regular alternation of non-REM sleep and REM sleep across a sleep period, in a cycle lasting 

approximately 90 minutes 

Rapid Eye Movement Sleep (REM Sleep) 

A type of sleep during which electrical activity of the brain resembles that during waking. However, 

from time to time the eyes move around under the closed eyelids – the ‘rapid eye movements’ – 

and this is often accompanied by muscle twitches and irregular heart rate and breathing. People 

woken from REM sleep can typically recall vivid dreaming. At the same time, the body cannot move 

in response to signals from the brain, so dreams cannot be ‘acted out’. The state of paralysis during 

REM sleep is sometimes known as the ‘REM block’. 

Recovery Sleep 

Sleep required for recovery from the effects of acute sleep loss (in one 24-hour period) or 

cumulative sleep debt (over multiple consecutive 24-hour periods). Recovery sleep may be slightly 

longer than usual, but lost sleep is not recovered hour-for-hour. Two nights of unrestricted sleep 

(when a crewmember is fully adapted to the local time zone) are typically required for recovery of 

normal sleep structure (non-REM/REM cycles). Recent laboratory research suggests that recovery 

of optimal waking function may take more than two nights of recovery sleep. 

*Rest Period 

A continuous and defined period of time subsequent to and/or prior to duty, during which flight or 

cabin crew members are free of all duties. 

Roster/Rostering 

Assignment of crewmembers to a schedule. 

Safety Management 

The systematic management of the operational risks associated with flight, engineering and ground 

activities in order to achieve as high a level of safety performance as is reasonably practicable. 

*Safety Management System (SMS) 

A systematic approach to managing safety, including the necessary organizational structures, 

accountabilities, policies and procedures. 
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Safety Performance 

The level of safety achieved in a risk controlled environment measured against a safety level 

deemed as low as reasonably practicable. 

Schedule 

Sequence of flights designed to meet operational requirements and effectively manage resources 

including crewmembers. 

Shift Work 

Any work pattern that requires a crewmember to be awake at a time in the circadian body clock 

cycle that they would normally be asleep. Problematic because the circadian body clock is sensitive 

to light and tends to remain ‘locked on’ to the day/night cycle rather than adapting to the work 

pattern. Shift work is usually associated with sleep restriction, together with a requirement to work 

during times in the circadian body clock cycle when performance and alertness are sub-optimal (for 

example, through the Window of Circadian Low). 

Sleep 

A reversible state in which conscious control of the brain is absent and processing of sensory 

information from the environment is minimal. The brain goes “off-line” to sort and store the day’s 

experiences and replenish essential systems depleted by waking activities. A complex series of 

processes characterized by alternation between two different brain states: non-REM sleep and 

REM sleep 

Sleep Debt 

See Cumulative sleep debt 

Sleep Disorders 

A range of problems that make it impossible to obtain restorative sleep, even when enough time is 

spent trying to sleep. More than 80 different sleep disorders have been identified, that can cause 

varying amounts of sleep disruption. Examples include obstructive sleep apnea, the insomnias, 

narcolepsy, and periodic limb movements during sleep 

Sleep Homeostatic Process 

The body’s need for slow-wave sleep (non-REM stages 3 and 4), that builds up across waking 

and discharges exponentially across sleep 

Sleep Inertia 

Transient disorientation, grogginess and performance impairment that can occur as the brain 

progresses through the process of waking up. Sleep inertia can occur on waking from any stage of 

sleep but may be longer and more intense on waking from slow-wave sleep (non-REM stages 3 

and 4), or after sleep periods or naps containing a high proportion of slow-wave sleep. 

Sleep Need 

The amount of sleep that is required on a regular basis to maintain optimal levels of waking 

alertness and performance. Very difficult to measure in practice because of individual differences. 

In addition, because many people live with chronic sleep restriction, when they have the 

opportunity for unrestricted sleep, their sleep may be longer than their theoretical ‘sleep need’ due 

to recovery sleep. 
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Sleep Quality 

Capacity of sleep to restore waking function. Good quality sleep has minimal disruption to the nonREM/REM cycle. Fragmentation of the non-REM/REM cycle by waking up, or by brief arousals that 

move the brain to a lighter stage of sleep without actually waking up, decreases the restorative 

value of sleep. 

Sleep Restriction 

Obtaining less sleep than needed (‘trimming’ sleep) across at least two consecutive nights. The 

effects of sleep restriction accumulate, with performance impairment and objective sleepiness 

increasing progressively. The need for sleep will eventually build to the point where people fall 

asleep uncontrollably (see micro-sleep). 

Slow-Wave Sleep 

The two deepest stages of non-REM sleep (stages 3 and 4), characterized by high amplitude slow 

brainwaves (EEG dominated by 0.5-4 Hz). 

Standby/standby duty 

A defined period of time, at the airport, at the hotel, or at home, during which a flight or cabin crew 

member is required by the Operator to be available to receive an assignment for a specific duty 

without an intervening rest period. 

Transient fatigue 

Impairment accumulated across a single duty period, from which complete recovery is possible 

during the next rest period. 

Trip 

A scheduling expression describing the time from when a crewmember initially reports for duty until 

he/she returns home from the sequence of flights and is released from duty. A trip may include 

multiple flights and many days of travel. 

Ultra long range operations (ULR) 

Augmented long range operations involving any sector between a specific city pair in which the 

planned flight time exceeds 16 hours, taking into account mean wind conditions and seasonal 

changes (as defined by the Ultra long range Crew Alertness Steering Committee, Flight Safety 

Foundation (2005). Flight Safety Digest 26.) 

Unforeseen operational circumstance 

An unplanned event, such as unforecast weather, equipment malfunction, or air traffic delay that is 

beyond the control of the operator. In order to be considered unforeseen, the circumstance would 

occur or become known to the operator after the flight has begun (after the moment the aeroplane 

first moves for the purpose of taking off) 

Unrestricted sleep 

Sleep which is not restricted by duty demands. Sleep can begin when a crewmember feels sleepy, 

and does not have to be delayed because of duty demands. In addition, the crewmember can wake 

up spontaneously and does not have to set the alarm to be up in time for duty. 

Window of Circadian Low (WOCL) 

Time in the circadian body clock cycle when subjective fatigue and sleepiness are greatest and 

people are least able to do mental or physical work. The WOCL occurs around the time of the daily 

low point in core body temperature - usually around 03:00-05:00 when a person is fully adapted to 

the local time zone. However, there is individual variability in the exact timing of the WOCL, which 

is earlier in morning-types (larks) and later in evening-types (owls), and may move a few hours later 

after consecutive night shifts. 
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 APPENDIX B: MEASURING CREWMEMBER FATIGUE 

FRM Processes (Chapter 4) and FRMS safety assurance processes (Chapter Five) sometimes 

require the measurement of crewmember fatigue. There is no single measurement that is the ‘gold 

standard’, because fatigue-related impairment affects many skills and has multiple causes. A wide 

variety of fatigue measures are used in scientific research. The measures described here are 

examples that have been chosen because: 

• they have been shown to be sensitive for measuring what they claim to measure (i.e., they 

have been scientifically validated); 

• they do not jeopardize crewmembers’ ability to perform their operational duties; and 

• they have been widely used in aviation, so data can be compared between different types of 

operations. 

New ways to measure fatigue and sleep are always being developed and some will become 

valuable tools to add to the list below, once they have been validated for use in aviation operations. 

Meanwhile, in an FRMS it is important to use measures that are accepted by regulators, operators, 

crewmembers, and scientists as being meaningful and reliable. This avoids the unnecessary cost 

and inconvenience of collecting data that is of doubtful value. 

Fatigue measurements can be based on crewmembers’ recall or current impressions of fatigue 

(subjective measures) or on objective measurements, such as performance tests and different 

types of physical monitoring. 

Each type of measure has strengths and weaknesses. To decide which types of data to collect, the 

most important consideration should be the expected level of fatigue risk. 

B1 CREWMEMBERS’ RECALL OF FATIGUE

B1.1 Fatigue Reporting Forms 

Fatigue reports allow individual crewmembers to give vital feedback on fatigue 

risks where and when they occur in an operation. Crew members are encouraged 

to do this through an effective safety reporting system (ICAO Doc 9859, SMS 

Manual). It is necessary to provide a clear understanding of the line between 

acceptable performance (which can include unintended errors) and unacceptable 

performance (such as negligence, recklessness, violations or sabotage). This 

provides fair protection to reporters but does not exempt them from punitive action 

where it is warranted. Crewmembers also need to be confident that reports will be 

acted on, which requires feedback from the Fatigue Safety Action Group, and need 

to be assured that the intent of the reporting process is to improve safety, not to 

attribute blame. A series of fatigue reports on a particular route can be a trigger for 

further investigation by the Fatigue Safety Action Group. 

Fatigue report forms need to be easy to access, complete, and submit. 

Consideration should be given to making fatigue report forms available for 

completion electronically, for example on lap top computers or smart phones (IPod, Blackberry, etc). The following example is adapted from a form that has been 

routinely used in an operator’s FRMS for more than 10 years. 

When fatigue report forms are first introduced, or other activities that raise fatigue 

awareness are launched, there is likely to be an increase in fatigue reporting. This 

‘spike’ does not necessarily represent an increase in fatigue occurrences or risk. It 

may simply be due to people being more likely to report. Other FRMS safety 

performance indicators may need to be evaluated, to decide whether the increase 

in reporting should trigger further action by the Fatigue Safety Action Group. 
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Fatigue Report Form
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B1.2 Retrospective Surveys 

Retrospective surveys are a comparatively cheap way to obtain information from a 

group of crewmembers on a range of topics such as: 

• demographics (age, flying experience, gender, etc); 

• amount and quality of sleep at home and on trips; 

• experience of fatigue on duty; and 

• views on the causes and consequences of fatigue on duty. 

Wherever possible, validated scales and standard questions should be used for 

gathering information on common topics such as sleep problems. This enables the 

responses of crewmembers to be compared across time, or with other groups. 17

For example, the Epworth Sleepiness Scale is a validated tool for measuring the 

impact of sleepiness on daily life. It is widely used clinically, to evaluate whether an 

individual is experiencing excessive sleepiness, 18 and information is available on 

its distribution in large community samples. 19 Figure B1 shows the Epworth 

Sleepiness scale. The crewmember is asked to rate each situation from 0=’would 

never doze’ to 3 ‘high chance of dozing’, for a total possible score of 24. Scores 

above 10 are generally considered to indicate excessive sleepiness. Scores above 

15 are considered to indicate extreme sleepiness. 

How likely are you to doze off or fall asleep in the following situations, in contrast to feeling just 

tired? This refers to your usual way of life in recent times.PLEASE TICK ONE BOX ON EACH LINE 

 would never slight moderate high 

 doze chance chance chance

Sitting and reading.....0 .......... 1 .......... 2 .......... 3 

 watching TV.....0 .......... 1 .......... 2 .......... 3 

 Sitting inactive in a public place (eg. theatre, meeting).....0 .......... 1 .......... 2 .......... 3 

 As a passenger in a car for an hour without a break.....0 .......... 1 .......... 2 .......... 3 

Lying down in the afternoon when circumstances permit...0 .......... 1 .......... 2 .......... 3 

Sitting and talking to someone.....0 .......... 1 .......... 2 .......... 3 

Sitting quietly after a lunch without alcohol.....0 .......... 1 .......... 2 .......... 3 

 In a car, while stopped for a few minutes in traffic.....0 .......... 1 .......... 2 .......... 3 

Figure B1: The Epworth Sleepiness Scale 

 

17 Note that some measures, for example the Karolinska Sleepiness Scale and the Samn-Perelli Crew Status Check 

are not designed to be used retrospectively. They are meant to be answered in relation to how you feel now. 

18 Johns MW (1994). Sleepiness in different situations measured by the Epworth Sleepiness Scale. Sleep 17:703-710. 

19 Gander PH, Marshall NS, Harris R, Reid P (2005). The Epworth sleepiness score: Influence of age, ethnicity and 

socioeconomic deprivation. Sleep 28:249-253 
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Retrospective surveys can also be used to track the effectiveness of an FRMS 

across time (i.e., as an FRMS safety assurance process – see Figure 5.3). 

Strengths and Weaknesses of Retrospective Surveys 

Retrospective surveys are a comparatively cheap way to gather a range of 

information. However, time and costs are involved in developing and distributing 

the survey questionnaire, entering the information into databases and analyzing it. 

A limitation of retrospective surveys is that the information gathered is subjective, 

and therefore its reliability is open to question. Reliability is a particular issue when 

crewmembers are asked to accurately recall details of past events, feelings, or 

sleep patterns. This is not to question crewmembers’ integrity – inaccurate recall of 

past events is a common and complex human problem. Concerns about whether 

some crewmembers might exaggerate in their responses, for personal or industrial 

reasons, should be minimal in a just reporting culture as is required for FRMS. In 

addition, extreme ratings are obvious when compared with group averages. 

Crewmembers’ confidence in the confidentiality of their data is likely to be a very 

important factor in their willingness to participate in surveys and to provide 

complete information on questionnaires. Despite limitations, retrospective surveys 

from time-to-time can be a useful source of information in an FRMS. 
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B2 MONITORING CREWMEMBER FATIGUE DURING FLIGHT OPERATIONS

B2.1 Subjective Fatigue and Sleepiness Ratings 

The following things should be considered when choosing rating scales for 

monitoring crewmember fatigue and sleepiness during flight operations. 

1. Is the scale quick and easy to complete? 

2. Is it designed to be completed at multiple time points, e.g., across a flight? 

3. Has it been validated? For example, has it been shown to be sensitive to the 

effects of sleep loss and the circadian body clock cycle under controlled 

experimental conditions? 

4. Is it predictive of objective measures such as performance or motor vehicle 

crash risk? 

5. Has it been used in other aviation operations, and are the data available to 

compare fatigue levels? 

The following two scales meet these criteria. 

The Karolinska Sleepiness Scale (KSS) 

This scale asks people to rate how sleepy they feel right now20. Any of the values 

from 1-9 can be ticked, not only those with a verbal description. 

Figure B3: The Karolinska Sleepiness Scale (KSS) 

 

20 Åkerstedt T, Gillberg M. Subjective and objective sleepiness in the active individual. Int J Neurosci 52: 29-37, 1990. 

 Gillberg M, Kecklund G, Åkerstedt T. Relations between performance and subjective ratings of sleepiness during a 

night awake. Sleep 17(3): 236-241, 1994. 

 Harma M, Sallinen M, Ranta R, Mutanen P, Muller K. The effect of an irregular shift system on sleepiness at work in 

train drivers and railway traffic controllers. J Sleep Res 11(2):141-151, 2002. 

 Gillberg M. Subjective alertness and sleep quality in connection with permanent 12-hour day and night shifts. Scand 

J Work Environ Health 24 (Suppl 3): 76-80, 1998. 

 Reyner LA, Horne JA. Evaluation of ‘in-car’ countermeasures to sleepiness: cold air and radio. Sleep 21(1): 46-50, 

1998. 

1 = extremely alert 

2 

3 = alert 

4 

5 = neither sleepy nor alert 

6 

7 = sleepy, but no difficulty remaining awake 

8 

9 = extremely sleepy, fighting sleep 
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Figure B4 shows KSS ratings from 25 flight crewmembers across ultra-long range 

flights from Singapore to Los Angeles. 21. 

12345678

Rating Time

2.00

4.00

6.00

8.00

S

el e

p

ni e

s

s

R

at ni g

?

$

?

$ ?

$ ?

$

?

$ ?

$

?

$

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Figure B4: KSS sleepiness ratings on flights from Singapore to Los Angeles 

Solid line – data for the command crew 

Dotted line – data for the relief crew 

 

21 Flight Safety Foundation (2006). Flight Safety Digest 24 (8-9). 

 Signal TL, van den Berg M, Travier N, Gander PH (2004). Phase 3 ultra-long range validation: in-flight 

polysomnographic sleep and psychomotor performance. Wellington, New Zealand: Massey University, Sleep/Wake 

Research Centre Report. 
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Each flight had two crews (two captains, two first officers). The command crew 

(solid line) flew both the take off and the landing and was allocated the 2nd and 4th

in-flight rest periods. The relief crew (dotted line) was allocated the 1st and 3rd inflight rest periods (they became the command crew for the return flight). 

Ratings were made at the following times: 

• rating 1 - pre-flight; 

• rating 2 - at top of climb; 

• rating 3 - before each crewmember’s 1st in-flight rest period; 

• rating 4 - after each crewmember’s 1st in-flight rest period; 

• rating 5 - before each crewmember’s 2nd in-flight rest period; 

• rating 6 – after each crewmember’s 2nd in-flight rest period; 

• rating 7 - at top of descent; and 

• rating 8 - post-flight before departing the aircraft. 

The command and relief crews have different patterns in their sleepiness ratings 

across the flight, partly as a result of their different in-flight rest periods. 

The Samn-Perelli Crew Status Check 

This scale asks people to rate their level of fatigue right now, and is a simplified 

version of the Samn-Perelli Checklist.22. 

Figure B5: The Samn-Perelli Crew Status Check 

 

22 Samn SW, Perelli LP. Estimating aircrew fatigue: A technique with implications to airlift operations. Brooks AFB, TX: 

USAF School of Aerospace Medicine. Technical Report No. SAM-TR-82-21, 1982. 

 Samel A, Wegmann HM, Vejvoda M, Drescher J, Gundel A, Manzey D, Wenzel J. Two-crew operations: Stress and 

fatigue during long-haul night flights. Aviat Space Environ Med 68: 679-87, 1997. 

 Samel A, Wegmann HM, Vejvoda M. Aircrew fatigue in long-haul operations. Accid Anal & Prev 29(4); 439-452, 

1997. 

1 = fully alert, wide awake 

2 = very lively, responsive, but not at peak 

3 = okay, somewhat fresh 

4 = a little tired, less than fresh 

5 = moderately tired, let down 

6 = extremely tired, very difficult to concentrate 

7 = completely exhausted, unable to function effectively 
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 Page 8 July 2011 

Figure B6 shows Samn-Perelli ratings for the same ULR crewmembers on the 

same flights as in Figure B4. 

12345678

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Figure B6: Samn-Perelli fatigue ratings on flights from Singapore to Los Angeles 

Solid line – data for the command crew 

Dotted line – data for the relief crew 

Strengths and Weaknesses of Subjective Ratings 

Subjective sleepiness and fatigue ratings are relatively cheap and easy to collect 

and analyze. Furthermore, how a crewmember feels is likely to influence their 

decisions about when to use personal fatigue countermeasure strategies. On the 

other hand, subjective ratings do not always reliably reflect objective measures of 

performance impairment or sleep loss, particularly when a person has been getting 

less sleep than they need (sleep restriction) across several consecutive nights. 

Concerns about some crewmembers exaggerating on subjective fatigue and 

sleepiness ratings, for personal or industrial reasons, should be minimal in a just 

reporting culture as is required for FRMS. In addition, extreme ratings are obvious 

when compared with group averages. 

In an FRMS, subjective sleepiness and fatigue ratings are particularly useful for: 

• gathering information from large groups of crewmembers; 

• where data are needed fairly quickly to decide whether more in-depth 

monitoring is warranted or if additional fatigue risk mitigation strategies are 

needed; and 

• among a range of measures when more intensive monitoring is undertaken in 

an FRMS (for example during validation of a new route), because they provide 

valuable insights on crewmembers’ experience of fatigue. 

Decision-making by the Fatigue Safety Action Group can be guided by comparing 

average (and/or extreme) ratings with data gathered on other operations. 
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July 2011 Page 9 

B2.2 Objective Performance Measurement 

A range of objective performance tests are used in laboratory studies, but they 

usually measure very specific aspects of performance (for example, reaction time, 

vigilance, short-term memory, etc), not the complex combinations of skills needed 

by crewmembers in the course of flight duties. Laboratory tests usually also 

measure the performance of individuals, not the combined performance of the 

crew. Nevertheless, some simple performance tests are considered ‘probes’ or 

indicators of a crewmember’s capacity to carry out his or her duties. 

The following things should be considered when choosing performance tests for 

monitoring crewmember fatigue and sleepiness during flight operations. 

1. How long does the test last? 

2. Can it be completed at multiple time points (e.g., a number of times across a 

flight), without compromising a crewmember’s ability to meet duty 

requirements? 

3. Has it been validated? For example, has it been shown to be sensitive to the 

effects of sleep loss and the circadian body clock cycle under controlled 

experimental conditions? 

4. Is it predictive of more complex tasks, e.g., crew performance in the simulator 

or during an in-flight emergency? (Unfortunately, there is very little research 

addressing this question at present.) 

5. Has it been used in other aviation operations, and are the data available to 

compare fatigue levels? 

One performance test that meets these criteria is the Psychomotor Vigilance Task 

or PVT. 23 In the most widely used version of the PVT, the test lasts for 10 minutes 

and is carried out on a purpose-built hand-held device. However, some recent 

studies 24 and large aviation field studies currently in progress are using a 5-

minute version of the PVT programmed on a Personal Data Assistant (PDA) 

device. 

Figure B7 shows mean reaction times on the PVT for the same ULR crewmembers 

on the same flights as in Figures B4 and B6. In this study, the 10-minute version of 

the test was used. PVT tests were done at the following times: 

• test 1 - close to top of climb; 

• test 2 - at the start of the second in-flight rest opportunity; 

• test 3 - close to top of descent; and 

• test 4 post-flight, before departing the aircraft. 

 

23 Dinges, D. F. and Powell, J. P. (1985). Microcomputer analysis of performance on a portable, simple visual RT task 

during sustained operation. Behavior Research Methods, Instruments, and Computing, 17: 652-655 

 Balkin, T. J., Bliese, P. D., Belenky, G., Sing, H., Thorne, D. R., Thomas, M., Redmond, D. P., Russo, M. and 

Wesensten, N. J. (2004). Comparative utility of instruments for monitoring sleepiness-related performance 

decrements in the operational environment. Journal of Sleep Research, 13: 219-227. 24 Lamond N, Petrelli, R, Dawson D, Roach GD. The impact of layover length on the fatigue and recovery of long-haul 

flight crew. Proceedings of the Fatigue in Transportation Conference (Session 13c), Seattle, September 11-25, 2005. 

US Department of Transport. 
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 Page 10 July 2011 

1234

Test Number

225.00

250.00

275.00

300.00

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Figure B7: Mean Reaction Time on the PVT Task on Flights from Singapore to 

Los Angeles 

Solid line – data for the command crew 

Dotted line – data for the relief crew 

Strengths and Weaknesses of the PVT 

The PVT requires a crewmember’s constant attention during the test. In the study 

in Figure B7, for example, this meant that crewmembers were required to be out of 

the operational control loop for a total of 30 minutes during the flight. This is an 

even greater challenge when crews are not augmented. 

In the study in Figure in B7, crewmembers were asked to complete PVT tests on 

the flight deck and there were clearly occasions when their attention was distracted 

by operational events. This increased the variability of performance on the PVT 

test across the group and made it more difficult to find statistically significant 

changes in PVT performance across the flight. Only the post-flight test (Test 4) in 

Figure B7 is significantly different from any of the others. 

The PVT does not measure important skills such as situation awareness and 

decision-making. On the other hand, more complex tests to measure these types 

of skills usually require many practice trials before they can be considered fully 

learnt and ready to be used for measuring changes due to fatigue. The PVT does 

not require practice trials, except to make sure that crewmembers know how to 

operate the testing device. 
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July 2011 Page 11 

B2.3 Monitoring Sleep 

Sleep loss is a key contributing factor to fatigue. In addition, crewmembers need to 

get recovery sleep to return to their optimum level of waking function. Sleep can be 

monitored during flight operations using subjective sleep diaries and/or by 

objective measures such as actigraphy or polysomnography. Each of these is 

described in more detail below. 

Sleep Diaries 

Sleep diaries ask crewmembers to record the following information about each 

sleep period: 

• where they sleep (home, layover hotel, in flight in a crew rest facility or a 

business class seat, etc); 

• what time they go to bed and get up; 

• how much sleep they think they get; and 

• how well they think they sleep. 

Crewmembers may also be asked to rate their sleepiness and fatigue before and 

after planned sleep periods. When sleep is being monitored during flight 

operations, crewmembers are also asked to record actual duty times. 

Diaries can have different layouts and they are often adapted to include specific 

information for a given study (for example, reminders about when to do 

performance tests or workload rating scales). Paper-based diaries are still more 

common, but electronic versions are also used (e.g., programmed on a PDA). 

Different layouts may be required for different parts of a study, for example pre-trip, 

during flights, and during layovers. 

Figure B8 shows an example of an in-flight sleep diary designed to be used during 

ultra-long range flight when crews have multiple in-flight rest periods (courtesy of 

the Sleep/Wake Research Centre). This example includes Karolinska Sleepiness 

and Samn-Perelli ratings before and after each sleep period, as well as a sleep 

quality rating scale for each sleep period. 
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Figure B8: Example of an in-flight sleep diary for ULR operations 

Strengths and Weaknesses of Sleep Diaries 

Sleep diaries are cheap compared to objective forms of sleep monitoring. 

However, information from paper diaries needs to be manually entered into 

databases, which can slow down the process of getting answers to a particular 

operational question, and analysis of diary data has costs associated. 

Sleep diaries are known to be less reliable than objective sleep monitoring. One 

study has compared sleep diaries and objective sleep measures from 21 B-777 

flight crewmembers in a layover hotel and in flight. 25 For in-flight sleep: 

• average sleep durations from diaries were similar to those recorded using 

polysomnography (the accepted gold standard for recording sleep); but 

• the variability among individuals was high. Some crewmembers overestimated how long they slept, and others underestimated; and 

• crewmembers’ estimates of how long they took to fall asleep, and their ratings 

of sleep quality were not reliably related to polysomnography measures. 

 

25 Signal, T.L., Gale, J., and Gander, P.H. (2005) Sleep Measurement in Flight Crew: Comparing Actigraphic and 

Subjective Estimates of Sleep with Polysomnography. Aviation Space and Environmental Medicine 76(11):1058-

1063 
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Thus diaries alone may be useful for measuring the sleep duration of groups but 

cannot be considered accurate for estimating the sleep duration of any one 

individual. In addition, diaries are not generally considered reliable for measuring 

sleep quality. (However, some very new research suggests that people’s reports of 

their sleep quality may be related to changes in parts of the brain that are not 

detected by polysomnography, so scientific opinion about the value of self-reported 

sleep quality may change). 

Despite these limitations, sleep diaries are a relatively cheap way of gathering 

reasonable information on the average amount of sleep obtained by groups of 

crewmembers. They are also used to help interpret objective sleep data, as 

described below. 

Actigraphy 

An actigraph is a small device worn on the wrist that contains an accelerometer to 

measure movement and a memory chip to store ‘activity counts’ at regular intervals 

(for example every minute). Depending on the amount of memory available, they 

can be worn for weeks to months before the data need to be down-loaded to a 

computer for analysis. Figure B9 shows an example of an older style actigraph. 

There are a number of manufacturers of actigraph devices, and each type comes 

with custom software that scans through the activity record and decides (based on 

a validated algorithm), whether the person was asleep or awake in each recorded 

epoch (for example every minute). Some devices have light sensors and some 

also have a regular watch face so that the wearer does not need to wear a normal 

watch as well, to keep track of time. 

Figure B10 shows an actigraphy record from a crewmember before, during, and 

after a Singapore-Los Angeles-Singapore ULR trip. Each vertical gray bar 

indicates an hour, with 24 hours (from midnight to midnight) plotted across the 

diagram. Consecutive days are shown down the page. The vertical black bars 

indicate the level of activity for each minute of the recording (higher bars indicate 

more movement). Periods with minimal movement (short, scattered black bars) 

correspond to times when the crewmember was asleep. 

Figure B9: an example of an actigraph 
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 Page 14 July 2011 

Figure B10 : Actigraphy record of a crewmember 

before, during, and after a Singapore-Los Angeles-Singapore ULR trip 

On the first Thursday, the crewmember in Figure B10 flew as a relief crewmember 

on the SIN-LAX segment, during which he had three in-flight rest opportunities (1 

hr 30 mins, 4 hrs, and 2 hrs), but (according to his diary) he only went to the crew 

rest facility for the 2nd of these. The actigraphy scoring algorithm calculated that he 

obtained 2hrs 55 mins of sleep during the 2nd rest period, and 1 hr 12 mins of sleep 

during his 3rd rest period, which he took in a passenger cabin. His sleep diary 

indicated that he also spent 44 minutes trying to sleep during his 1st rest period, but 

the algorithm could not (at that time) score such a short sleep period. 

The following Sunday, he flew as a command crewmember on the LAX-SIN 

segment and had two in-flight rest opportunities (195 minutes and 300 minutes), 

both of which he took in the crew rest facility. According to the actigraphy scoring 

algorithm, he obtained 2 hrs 14 min of sleep in his 1st rest period and 4 hrs 3 min in 

his 2nd rest period. 
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Strengths and Weaknesses of Actigraphy 

As Figure B10 illustrates, actigraphy is very useful for obtaining objective records 

of the sleep/wake patterns of crewmembers across multiple days. This is currently 

the most practical and reliable way to look at whether a crewmember accumulates 

a sleep debt across a line of flying, compared to the amount of sleep they average 

when off duty. Actigraphy can also provide useful information on recovery sleep 

after a trip. 

Actigraphs are small and unobtrusive to wear, and actigraphy is cheap compared 

to polysomnography. The main limitation of actigraphy is that it monitors activity 

(not sleep) and it cannot distinguish between someone being asleep versus being 

awake but not moving. 

The study described previously 9 also compared actigraphy and polysomnographic 

sleep recordings from the 21 B-777 flight crewmembers. For both hotel sleep and 

bunk sleep: 

• average sleep durations calculated from actigraphy were similar to those 

recorded using polysomnography; but 

• for individual crewmembers, actigraphy could overestimate or underestimate 

polysomonographic sleep duration by more than an hour. This amount of 

inaccuracy is particularly problematic for in-flight sleep periods, which tend to 

be short; and 

• comparing actigraphy and polysomnography minute-by-minute, the study 

concluded that actigraphic estimates of how long crewmembers took to fall 

asleep, and of how often they woke up during a sleep period (sleep quality), 

were not reliably related to polysomnographic measures. 

On the positive side, the study demonstrated that actigraphy was not significantly 

contaminated by in-flight factors such as turbulence or aircraft movement, and that 

it is reliable for estimating the average sleep duration of groups of crewmembers, 

both in the air and on the ground. 

Actigraphs are currently not particularly cheap, although some manufacturers are 

working on new generation devices that may push costs down. Not all actigraphs 

on the market have been validated (by comparing their algorithms for estimating 

sleep quantity and quality with polysomnography), and some have not yet been 

demonstrated to be robust and reliable for sleep monitoring during flight operations 

(battery life can be a problem in some devices). 

At present, the accepted standard for analyzing actigraphy records is to use a 

sleep diary to identify when a crewmember was trying to sleep (as opposed to just 

sitting still or not wearing the watch). The sections of the record where the 

crewmember was trying to sleep are then analyzed for sleep duration and quality. 

This type of analysis requires a trained person to work through actigraphy records 

manually, which is time consuming and fairly costly. Several manufacturers and 

research groups are looking at ways to bypass the need for this manual scoring, 

which would make actigraphy much cheaper and faster to analyze. However, the 

reliability of these new approaches for estimating sleep quantity and quality 

(compared to polysomography) remains to be demonstrated. 

Some operators may choose to develop the capacity in-house to collect and 

analyze actigraphy. As part of the FRMS Assurance Processes, an external 

scientific advisory group could be convened periodically to review the actigraphy 

analyses and the resulting decisions made by the Flight Safety Action Group. 
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 Page 16 July 2011 

Polysomnography 

Polysomnography is the accepted gold standard for monitoring sleep and is 

currently the only method that gives reliable information on the internal structure of 

sleep and on sleep quality. It involves sticking removable electrodes to the scalp 

and face and connecting them to a recording device, to measure three different 

types of electrical activity: 1) brainwaves (electroencephalogram or EEG); 2) eye 

movements (electroculogram or EOG); and 3) muscle tone (electromyogram or 

EMG). 

In addition to monitoring sleep, polysomnography can be used to monitor waking 

alertness, based on the dominant frequencies in the brainwaves, and patterns of 

involuntary slow rolling eye movements that accompany sleep onset. Figure B11 

shows a flight crewmember on the flight deck wearing polysomnography 

electrodes, which the researcher is connecting to a portable recording device. 

Figure B11: Polysomnographic recording in flight 
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Figure B12 shows an analysis of the polysomnography record of the 1st in-flight 

sleep period on the SIN-LAX flight for the same crewmember whose actigraphy 

record is shown in Figure B10 (times in UTC). Figure B12 is a graph created by a 

trained sleep technician who has gone through the entire polysomnographic 

recording and, using an internationally agreed set of rules, has decided for each 30 

seconds whether the crewmember was awake, or in which type of sleep he spent 

most of that 30 seconds. Figure B12 shows that he took 13 minutes to fall asleep 

and then spent a total of 17.5 minutes in light non-REM sleep (S1 and S2). 

However, he woke up 6 times across the sleep period. He did not enter deep nonREM sleep (S3 and S4), or Rapid Eye Movement (REM) sleep. 

9:15 a.m. 9:20 a.m. 9:25 a.m. 9:30 a.m. 9:35 a.m. 9:40 a.m. 9:45 a.m. 9:50 a.m. 9:55 a

S4

S3

S2

S1

REM

Wake

MT

Stages

Figure B12: Polysomnographic record for the 1st in-flight rest period on the SINLAX flight (same crewmember as in Figure B10) 

Figure B13 shows the polysomnographic record for the same crewmember during 

his 2nd in-flight rest period on the SIN-LAX flight. In this rest period (in the bunk), he 

fell asleep in 19.5 minutes and then slept for a total of 144.5 minutes, interrupted 

by numerous brief periods of waking which totaled 52 minutes. He spent 1.5 

minutes in deep non-REM sleep (S3), 2 minutes in REM sleep, and the rest of the 

time in light non-REM sleep (S1 and S2). 

1:40 p.m. 2:00 p.m. 2:20 p.m. 2:40 p.m. 3:00 p.m. 3:20 p.m. 3:40 p.m. 4:00 p.m. 4:20 p.m. 4:40 p.m. 5:00 p.m

S4

S3

S2

S1

REM

Wake

MT

Stages

Figure B13: Polysomnographic record for the 2nd in-flight rest period on the SINLAX flight (same crewmember as in Figure B10) 
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 Page 18 July 2011 

Strengths and Weaknesses of Polysomnography 

Figures B12 and B13 show the detailed information about sleep quality that can 

only be obtained from polysomnographic recordings. When it is important to be 

certain about the amount and type of sleep that crewmembers are obtaining, 

polysomnographic monitoring is the most trusted method. 

On the other hand, polysomnography is relatively obtrusive and time-consuming. It 

takes a well-trained technician about 30 minutes to attach the recording electrodes 

to a person’s scalp and face, and check that all the electrical connections are 

working. For in-flight recordings, the electrical contacts need to be checked 

periodically (for example before each in-flight rest period) to make sure that the 

signals are still clean. Crewmembers can be shown how to remove the electrodes 

themselves. However, the equipment is expensive and fragile and a technician is 

required to download the data from the recording device to a computer, and to 

clean the equipment. This means that it is usual for at least one technician to 

accompany crewmembers throughout a trip during which their sleep is recorded 

using polysomnography. This is costly. 

As previously mentioned, the currently accepted standard for analyzing 

polysomnography is to have a trained sleep scoring technician work through the 

entire recording to decide for each 30 seconds whether the crewmember was 

awake, or in which type of sleep he/she spent most of that 30 seconds. For quality 

assurance, it is usual to have a second trained technician score at least some of 

the records to check the reliability of scoring between the two technicians. This is 

time consuming and relatively expensive. A number of groups are working on 

automated scoring systems for polysomnography, but as yet none of these are 

widely accepted by the sleep research and sleep medicine communities. Beyond 

the scoring process, it is necessary to have a qualified person to interpret that 

significance of diagrams such as Figures B12 and B13. 

Despite these costs and inconveniences, there have been a number of studies of 

flight crew sleep that have used polysomnography and these have been very 

informative. While it is unlikely that any airline would need to develop in-house 

capacity to record and analyze polysomnography as a routine part of its FRMS, 

there are situations where the detailed information from polysomnography is 

needed. For example, in launching the first commercial passenger ULR flights, 

Singapore Airlines and the Singapore Civil Aviation Authority agreed that a 

subgroup of crewmembers would have their sleep monitored by polysomnography 

during the operational validation of the SIN-LAX route. The data in Figures B4, B6, 

B7, B10, B12, and B13 come from this validation and are used with the kind 

permission of the Singapore Civil Aviation Authority (Dr Jarnail Singh) and 

provided by the Sleep/Wake Research Centre at Massey University, New Zealand. 
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B2.4 Monitoring the Circadian Body Clock Cycle 

The circadian body clock cycle is a key contributing factor to crewmember fatigue, 

but it is difficult to monitor during flight operations. In the laboratory, the cycle of the 

body clock is usually monitored by measuring two of the overt rhythms that it 

drives; 

1. the daily rhythm in core body temperature; and 

2. the daily rhythm in levels of the hormone melatonin, which is secreted by the 

pineal gland at night. Melatonin levels can be measured from blood, saliva, or 

urine samples collected at regular intervals. 

During the 1980s, a number of research teams monitored the circadian body 

clocks of crewmembers by tracking the rhythm of core body temperature. Figure 

B14 shows the times of the daily temperature minimum of one participating B-747 

crewmember across an 8-day long-haul trip pattern. 26

At home in SFO prior to the trip, his temperature minimum (inverted triangle) 

occurred about 5 hours into his sleep period (black horizontal bar). During the trip, 

he repeatedly flew westward then back eastward across multiple time zones, 

spending around 24 hours in each location. The circadian temperature minimum 

could not follow this disrupted pattern (it shifted by no more than 2 hours from one 

day to the next). Across the trip pattern, it drifted progressively later, so that by the 

time the crewmember arrived back in SFO at the end of the trip, it had drifted about 

6 hours later. Thus, when he got home, the crewmember’s circadian body clock 

was 6 hours out of step with his home time zone and took several days to readapt. 

Another interesting feature of this record is that the temperature minimum (when 

physiological sleep drive is highest), sometimes occurs in flight, for example on the 

flight from NRT to HKG. At these times, the crewmember is at greatest risk of 

falling asleep unintentionally on the flight deck. Alternatively, if he has the 

opportunity for a rest break (which was not the case in this operation), this would 

represent a very good time to try to get some in-flight sleep. 

 

26 Gander, P.H., Gregory, K.B., Miller, D.L., Rosekind, M.R., Connell, L.J., and Graeber, R.C. (1998) Flight crew fatigue 

V: long-haul air transport operations. Aviation, Space, and Environmental Medicine 69:B37-B48 
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 Page 20 July 2011 

Figure B14: Sleep times (diary data) and times of the circadian temperature 

minimum of a crewmember during a long haul trip pattern. 

Clearly, Figure B14 provides valuable information that can be related to the 

crewmember’s sleep, fatigue, mood, and performance capacity. However, it has 

been several decades since this type of monitoring has been undertaken primarily 

because of the logistics and cost of tracking circadian rhythms during flight 

operations. 

There is ongoing research aimed at developing more robust and less intrusive 

methods for continuously monitoring circadian rhythms outside the laboratory, 

including a new generation of temperature ‘pills’, that are swallowed and transmit 

temperature measurements as they transit through the digestive system. However, 

body temperature is also affected by the level of physical activity, and it is complex 

to separate out this ‘masking effect’ from the actual circadian clock-driven 

component of the temperature rhythm (this was done mathematically in Figure 

B14). 

Sleep (from diary) 

Flight 

Local night 

Nap 

Temperature minimum
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The second rhythm that is commonly monitored in the laboratory to track the cycle 

of the circadian body clock is the level of the hormone melatonin. Melatonin can be 

measured in blood or saliva samples taken at regular intervals, and its metabolites 

can be measured in urine samples. There are obvious difficulties associated with 

collection and frozen storage of body fluid samples during flight operations. 

Another complicating factor is that synthesis of melatonin is switched off by bright 

light. Thus, if a crewmember is exposed to daylight during his/her “biological night” 

(for example, a few hours either side of the of the temperature minimum in Figure 

B14), melatonin secretion will stop. This makes it impossible to track its normal 

circadian cycle cross a trip such as that in Figure B14. Analyzing for hormone 

levels in body fluids is a highly skilled task that needs to undertaken by a reputable 

laboratory. 

Strengths and Weaknesses of Monitoring the Circadian Body Clock Cycle 

There is remarkably little information available on how the circadian body clock is 

affected by any kind of flight operations. Where data have been collected, there is 

evidence of considerable variability between individuals on the same trip patterns. 

Better information in this area would improve the predictive power of biomathematical models for fatigue hazard identification, and might provide insights 

on how to tailor personal mitigation strategies for crewmembers who are morningtypes versus evening-types. A number of groups are actively working on new 

technologies for monitoring the circadian body clock cycle, but as yet none of these 

has been validated or demonstrated to be robust enough and practical for use 

during flight operations. 

B3 EVALUATING THE CONTRIBUTION OF FATIGUE TO SAFETY EVENTS

There is no simple formula for evaluating the contribution of crewmember fatigue to a safety 

event. For the purposes of the FRMS, the aim is to identify how the effects of fatigue could 

have been mitigated, in order to reduce the likelihood of similar occurrences in the future. 

Basic information can be collected for all fatigue reports and safety events, with more indepth analyses reserved for events where it is more likely that fatigue was an important 

factor and/or where the outcomes were more severe. 

To establish that fatigue was a contributing factor in an event, it has to be shown that; 

• the person or crew was in a fatigued state; and 

• the person or crew took particular actions or decisions that were causal in what went 

wrong; and 

• those actions or decisions are consistent with the type of behaviour expected of a 

fatigued person or crew 

In 1997, the Canadian Transportation Safety Board produced guidelines for fatigue analysis. 

They suggest four initial questions to decide whether or not fatigue was a contributing factor 

to an event. 27

1. At what time of day did the occurrence take place? 

2. Was the crewmember’s normal circadian rhythm disrupted? 

3. How many hours had the crewmember been awake at the time of the occurrence? 

4. Does the 72-hour sleep history suggest a sleep debt? 

 

27 Transportation Safety Board of Canada, 1997. A Guide for Investigating for Fatigue. Transportation Safety Board of 

Canada, Gatineau, Quebec. 
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If the answer to any one of these questions indicates a problem, then fatigue should be 

investigated in greater depth. This requires working through two checklists (adapted from the 

Canadian Transportation Safety Board guide). 

Checklist 1 is designed to establish whether the person or crew were in a fatigued state, 

based on a series of questions or probes that address key aspects of fatigue. The answer to 

each question is compared to the best case response, in order to build an overall picture of 

the fatigue hazard. Any departure from the best case response indicates increased risk of 

fatigue. 

Checklist 2 is designed to establish whether the unsafe action(s) or decision(s) were 

consistent with the type of behaviour expected of a fatigued person or crew. 
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Checklist 1: Establishing the Fatigued State
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 Page 24 July 2011 

Checklist 1: Establishing the Fatigued State (continued) 
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Checklist 2: Establishing the Link between Fatigue and the Unsafe Act(s)/Decision(s)
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Checklist 2: Establishing the Link between Fatigue and the Unsafe Act(s)/Decision(s) (continued) 
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APPENDIX C

July 2011 Page 1 

 APPENDIX C: PROCEDURES FOR CONTROLLED REST ON THE FLIGHT DECK 

Controlled rest on the flight deck is an effective fatigue mitigation for flight crews. It should not be 

used as a scheduling tool. It is not a substitute for proper preflight sleep or for normal crew 

augmentation, but intended as a response to unexpected fatigue experienced during operations. 

Some basic principles: 

x It should be considered a safety net. 

x The Fatigue Safety Action Group should be able to monitor the use of controlled rest on the 

flight deck to evaluate whether existing mitigation strategies are adequate. Crew reports are 

encouraged. 

x It should only be used on flights of sufficient length that it does not interfere with required 

operational duties. 

x It should only be used during low workload phases of flight (e.g., during cruise flight). 

x It should not be used as a method for extending crew duty periods. 

x Procedures for controlled rest on the flight deck should be published and included in the 

Operations Manual. 

Recommended Procedures for Controlled Rest on the Flight Deck 

The following recommended procedures are based on a survey of major air carriers. They 

represent considerable experience in many regions of the globe and include options reflecting 

variations between different types of operations. 

Note: this is not intended to be an all inclusive list, nor are all of these procedures necessarily 

required. Each operator should work with their regulator to define appropriate procedures. 

x Only one pilot may take controlled rest at a time in his/her seat. The harness should be used 

and the seat positioned to minimize unintentional interference with the controls. 

x The autopilot and auto-thrust systems (if available) should be operational. 

x Any routine system or operational intervention which would normally require a cross check, 

should be planned to occur outside controlled rest periods. 

x Controlled rest on the flight deck may be used at the discretion of the captain to manage both 

unexpected fatigue and to reduce the risk of fatigue during higher workload periods later in the 

flight.

x It should be clearly established who will take rest, and when it will be taken. If the pilot in 

command requires, the rest may be terminated at any time. 

x The pilot in command should define criteria for when his/her rest should be interrupted. 

x Hand-over of duties and wake-up arrangements should be reviewed. 

x Flight crews should only use controlled rest if they are familiar with the published procedures. 

x Some operators involve a third crewmember (not necessarily a pilot) to monitor controlled 

flight deck rest. This may include a planned wake-up call, a visit to be scheduled just after the 

planned rest period ends, or a third crewmember on the flight deck throughout controlled rest. 

x The controlled rest period should be no longer than 40 minutes, to minimize the risk of sleep 

inertia on awakening. 
FATIGUE RISK MANAGEMENT SYSTEM (FRMS) 

IMPLEMENTATION GUIDE FOR OPERATORS 

APPENDIX C 

 Page 2 July 2011 

x Controlled rest should only be utilized during the cruise period from the top of climb to 20 

minutes before the planned top of descent. This is to minimize the risk of sleep inertia. 

x A short period of time should be allowed for rest preparation. This should include an 

operational briefing, completion of tasks in progress, and attention to any physiological needs 

of either crew member. 

x During controlled rest, the non-resting pilot must perform the duties of the pilot flying and the 

pilot monitoring, be able to exercise control of the aircraft at all times and maintain situational 

awareness. The non-resting pilot cannot leave his/her seat for any reason, including 

physiological breaks. 

x Aids such as eye shades, neck supports, ear plugs, etc., should be permitted for the resting 

pilot.