Evaluation of Fatigue in Short-Haul Operations Across Multiple Airlines
Conditions: Fatigue
Sponsor: Civil Aerospace Medical Institute

1. Title: Evaluation of Fatigue in Short-Haul Operations Across Multiple Airlines 
2. Organizations and Study Location(s): The research described will be performed by investigators at 
NASA Ames Research Center (ARC) in collaboration with researchers at the Civil Aerospace Medical 
Institute (CAMI), Washington State University (WSU), and Brigham and Women’s Hospital (BWH). Due to 
the nature of the project, field data will be collected throughout the United States (US). 
3. Investigator: 
Erin E. Flynn-Evans, PhD MPH 
NASA Ames Research Center 
 
 
 
Human Systems Integration Division 
Mail Stop 262-4, Code TH 
Moffett Field, CA 94035 
Phone: (650) 279-3459 
Fax: (650) 604-3729 
Email: erin.e.flynn-evans@nasa.gov 
 
Co-Investigators: 
Cassie J. Hilditch, PhD 
San José State University 
NASA Ames Research Center 
 
 
 
Human Systems Integration Division 
Mail Stop 262-4, Code TH 
Moffett Field, CA 94035 
Email: cassie.j.hilditch@nasa.gov  
 
Nicholas G. Bathurst, MA 
NASA Ames Research Center 
 
 
 
Human Systems Integration Division 
Mail Stop 262-4, Code TH 
Moffett Field, CA 94035 
Email: nicholas.g.bathurst@nasa.gov  
 
Collaborators: 
Thomas Nesthus, PhD 
FAA Aviation Safety 
Civil Aerospace Medical Institute (CAMI) 
Oklahoma City, OK 73169 
Email: tom.nesthus@faa.gov 
Hannah Baumgartner, PhD 
FAA Aviation Safety 
Civil Aerospace Medical Institute (CAMI) 
Oklahoma City, OK 73169 
Email: hannah.m.baumgartner@faa.gov 
 
Amanda Lamp, MS, PhD 
Washington State University (WSU) 

Occupational Sleep Medicine Group 
Email: alamp@wsu.edu  
 
Laura Barger, PhD 
Brigham & Women’s Hospital 
Harvard Medical School 
Division of Sleep Medicine 
Boston, MA 02115 
Email: laura_barger@hms.harvard.edu 
 
Heather Provost 
Senior Manager, Fatigue Risk Management 
American Airlines 
Fort Worth, TX 76155 
Email: heather.provost@aa.com  
 
Fatigue Countermeasures Laboratory Study Staff: 
Lucia Arsintescu (SJSU Research Foundation) 
Kevin Gregory (NASA) 
Nathan Feick (SJSU Research Foundation) 
Crystal Kirkley (NASA) 
Gregory Costedoat (SJSU Research Foundation) 
Zachary Glaros (NASA) 
Sean Pradhan (Menlo College) 
Rachel Jansen (SJSU Research Foundation) 
David Rockman (SJSU Research Foundation) 
Michelle Tripp (SJSU Research Foundation) 
 
WSU Research Team: 
Kylee Dawn Amos 
Michael Rempe 
Ian Rasmussen 
 
AA Research Team: 
Lucas Johnson 
 
4. Purpose 
This research is being conducted as a component of a Reimbursable Interagency Agreement between 
NASA and CAMI (IAA No. SAA2-403611). The purpose of the present study is to collect objective and 
subjective measures of sleep, sleepiness, performance, and workload that can be used to assess fatigue 
levels of short-haul pilots during normal operations. 
5. Background 
Aviation regulation and safety oversight is in an era of performance-based risk management. Research is 
ongoing to understand the role fatigue plays in degraded human performance during various types of 

operations within the aviation system. As part of this process, the Federal Aviation Administration (FAA) 
proposed duty limits and rest requirements which went into effect in 2014 (Code of Federal Regulations 
[14 CFR] Part 117, 2012). A study of fatigue in short-haul operations under these regulations is yet to be 
conducted. Recently, the FAA proposed the need for research to evaluate fatigue within these 
regulations in short-haul operations.  
Determinants of Alertness and Performance in Short-Haul Aviation Operations 
There has been a great deal of research to understand the influence of factors such as circadian 
misalignment induced by jet lag during long-haul flights on pilot fatigue and performance, but 
comparatively fewer studies have been conducted to evaluate fatigue and performance among pilots 
during short-haul operations. There are several factors that have the potential to reduce alertness and 
performance among airline pilots during short-haul operations, including time of day, time awake, 
workload, and consecutive work shifts. Each of these factors can influence a pilot’s fatigue and 
performance, and in combination, these factors have the potential to cause severe performance 
impairment. 
Time of Day. The circadian rhythm promotes waking during the biological day and sleep at night. When 
individuals who are normally awake during the day and sleep at night have to engage in night work, the 
sleep drive is strongest and performance is worst during the hours of 0200 to 0559, a time that has been 
dubbed the Window of Circadian Low (WOCL; Scientific Principles for Fatigue Management, 2015). Prior 
studies confirm that micro-sleeps and fatigue ratings are highest during night flights (Samel et al., 1997), 
whereas performance is relatively stable during short-haul flights that occur during the day when the 
circadian rhythm is strongly promoting wakefulness (Flynn-Evans et al., 2018). 
Start Time of Duty and Time Awake. The start time and time awake prior to a flight can also influence 
an individual’s ability to obtain adequate sleep and maintain subsequent performance. Consecutive 
early work start times can lead to WOCL encroachments and lower quality sleep (Roach et al., 2012; 
Flynn-Evans et al., 2018), while later report times could mean pilots may wake several hours prior to 
their actual duty, increasing time awake before performing critical tasks (Rosekind et al., 1994; Samel et 
al., 1997; Gander et al., 1998; Caldwell et al., 2006; Vejvoda et al., 2014). Indeed, short-haul pilots who 
start work in the morning after 0900 have been shown to achieve more sleep (Roach et al., 2012; Flynn-
Evans et al., 2018).  
Flight Segments. Workload can also influence a pilot’s fatigue level. Several studies have demonstrated 
that flying three or more flight segments in a single duty day is associated with increased subjective 
ratings of fatigue and poorer performance (Bourgeois-Bougrine et al., 2003; Powell et al., 2007; Honn et 
al., 2016). 
Consecutive Operations. Several studies have demonstrated that working consecutive days is associated 
with poorer performance. For example, Flynn-Evans et al. (2018) found that pilots performed worse 
with each consecutive day of flying when scheduled for early starts, long midday flights, and late 
finishing daytime flights. 
Preliminary Data: Focus Group Study 
In order to identify fatigue factors of greatest importance to study, we conducted a series of focus 
groups across four major commercial passenger airlines in the United States. This study revealed several 

operations that pilots identified as fatiguing (Table 1). We combined these themes into six over-arching 
categories including: circadian disruption, high workload, rest opportunity, schedule changes, 
regulations, and long sits. While categories provide a useful summarization of the overall content, the 
value of the qualitative approach is the resolution of data at theme and code level. Therefore, core 
themes and CODES contributing to these categories are described below. 
Table 1. Themes ranked by frequency of codes within each theme.  
Theme 
N 
% 
Circadian switches 
171 
10.5 
Rest duration (layover) 
153 
9.4 
High workload / Hassle factors 
151 
9.3 
Number of flights 
121 
7.4 
FAR 117 issues 
93 
5.7 
Long sits 
85 
5.2 
Redeyes 
83 
5.1 
Unpredictability 
79 
4.9 
Aircraft & crew swaps 
73 
4.5 
Rest timing 
73 
4.5 
Out-of-hours work 
68 
4.2 
Early duties 
64 
3.9 
Short turn time 
53 
3.3 
Length of duty 
46 
2.8 
Rest quality 
45 
2.8 
Schedule design 
38 
2.3 
Trip length 
37 
2.3 
Late duties 
25 
1.5 
Fatigue calls 
24 
1.5 
Length of flights 
20 
1.2 
Rest - Circadian disruption 
20 
1.2 
Deadhead 
14 
0.9 
Total 
1625*   
 
Note: * = total includes codes that did not fit a defined theme. Percentage column reflects the 
proportion of all codes counted within each theme. 
 
Circadian disruption. This category includes all themes related to inconsistent schedules (Circadian 
switches), duties outside of daytime hours (Redeyes, Early duties, Late duties, Out-of-hours work), rest 
opportunities during the day (Rest timing), and rest breaks that involve a circadian switch between 
duties (Rest – circadian disruption). 
The most common theme identified overall, Circadian switches, refers to changes in duty start times 
within a trip, for example switching from an early start time to a late start time. This theme was made 
up of codes including: CIRCADIAN SWAPS (34% of codes in this theme), INCONSISTENT DUTY TIMES 

(25%), and SWITCHING TIME ZONES (18%). SWITCHING TIME ZONES refers to the sentiment that while a 
schedule may look consistent based on local departure times, similar local start times in different time 
zones could lead to circadian shifts of up to three hours. For example, a west coast-based pilot may start 
day 1 of a trip at 0600h on Pacific Time (PT) and then have a 0600h report time on day 2 on Eastern 
Time (ET), which is effectively 0300h PT. 
High workload. This category includes all themes related to increased workload such as High workload 
& hassle factors, Number of flights, Aircraft & crew swaps, Short turn times, and Length of flights. The 
third most common theme identified overall was High workload & hassle factors, which refers to a 
collection of operational challenges contributing to fatigue. Often these factors add to overall workload 
through increased mental effort or creating time pressure and not allowing for mental recovery during 
or between flights. Some factors also extend duty times, leading to extended time awake and reduced 
rest opportunity. This theme was made up of codes including: WEATHER (30%), MAINTENANCE (19%), 
GROUND OPS (18%), and BUSY AIRPORTS/REGIONS (14%).  
This category also includes the fourth most common theme, Number of flights. This theme refers to the 
number of flights within a duty period. While long-haul operations typically only involve one flight within 
a duty period, short-haul operations typically include two or more flights within a duty period. Most 
responses within this theme (41%) indicated that duty periods with more than four flights were 
considered fatiguing. However, approximately one-third (36%) of the codes in this theme indicated a 
preference for duty periods with two or fewer flights in order to avoid fatigue, with a quarter (23%) 
suggesting that any duty with more than one flight is automatically fatiguing due to the nature of the 
operations. 
Rest opportunity. This category includes themes related to rest opportunities independent from the 
timing of those opportunities (see Circadian disruption for Rest timing) including Rest Duration 
(Layover) and Rest quality. Rest quality covered codes related to hotel sleep environment (e.g., noise, 
temperature). Rest duration (layover) was the second most common theme and refers to insufficient 
rest opportunity between duties. This theme was made up of codes including: SHORT REST (42%), and 
PERSONAL TIME (30%). SHORT REST referred to comments indicating that the FAR 117 minimum rest 
requirement of 10 hours is too short for sufficient sleep opportunity. PERSONAL TIME includes 
comments regarding the need for time to eat, exercise, wind down, and prepare for the next duty within 
the allocated rest period. In a short rest period, often there is not enough time for all these factors, 
leading to skipping important daily needs and/or reducing the amount of time available for sleep. 
Schedule changes. This category emerged from the theme, Unpredictability, which covered codes such 
as SCHEDULE CHANGES (43%), PLANNED VS OPS (29%, planned schedules being different to operational 
reality), and EXTENSIONS and DIVERSIONS (28%). Schedule changes affected fatigue by extending flight 
or duty time, adding workload, and/or changing the timing of duty and rest opportunities.  
Regulations. This category includes the fifth most common theme, FAR 117 issues, as well as Fatigue 
Calls. FAR 117 issues refers to comments from participants regarding the regulations (FAR 117) dictating 
the current flight, duty, and rest time requirements and how they are implemented. Thirty-seven 
percent of the codes in this theme related to the use of FAR regulations by airlines as goals or targets, 
rather than limits. A further 24% recommended revisions to the regulations in order to effectively 
manage fatigue. Some participants felt that the scheduling software used to create pairings lacked 
human insight into obviously fatiguing duties and trips. With regard to Fatigue Calls, participants 

commented on barriers to submitting fatigue calls (BARRIERS, 42%) such as lack of pay protection and 
the drive to “get the job done”. A third of codes in this theme (RESPONSIBILITY, 33%) reflected the 
pilots’ disagreement with the fatigue call system putting the responsibility on the pilot to call out 
fatigued, and felt that more responsibility should lie with the airline to provide less fatiguing schedules.  
Long sits. This category emerged from the theme, Long Sits, which in turn was derived from the code 
LONG SITS. Sit time refers to the time between flights within a duty during which the pilot has to wait in 
the airport until the next flight. The general consensus among participants was that a long sit would be 
defined as a sit time greater than 2 hours. The concept of long sits was so prevalent in the transcripts, 
that despite not being merged with any other codes, it was the sixth most common theme. The concept 
was also unrelated to the other themes, hence warranting its own category in order to capture this 
unique concept.  
It is difficult to study the impact of so many factors on fatigue because the series of flights that pilots are 
scheduled for, known as a trip, can include factors that make data aggregation difficult without an 
enormous sample size. As a result, it is necessary to collect data on targeted operations in order to 
evaluate the impact of the most disruptive factors on fatigue. Hence, our primary aim is to compare 
sleep, sleepiness, performance, and workload during trips with circadian disruption to trips without 
circadian disruption. We will collect observational data on the other factors that were identified in the 
focus groups in order to help inform future research in those areas. We will study participants during 
their normal scheduled operations.  
6. Why Human Research is Required  
Human research is required because there are no other reliable, efficient, and cost-effective methods 
for obtaining such information from animal or modeling sources. Only performance by humans is 
possible or relevant. 
7. Conflict of Interest 
Do any of the participating study investigators or other research personnel (or their immediate 
family/significant other) have a financial and/or intellectual property interest in the sponsor or products 
used with this project? 
 
____Yes __X__No 
8. Plan of Study 
8.1 Protocol Overview 
Scientific Merit. Please see attached ARC476 for scientific review and approval. 
Specific Aims. The goal of this study is to provide insight into the influence of trips including circadian 
disruption on pilot cognitive performance, fatigue, sleepiness, sleep, and workload during short-haul 
operations across multiple airlines. 
Hypotheses. 

We aim to study pilots completing trips that include circadian disruption compared to trips that do not 
include circadian disruption.  
• 
We hypothesize that cognitive performance, fatigue, sleepiness, and sleep outcomes will be 
worse during circadian disrupted trips compared to trips that do not involve circadian 
disruption.  
Primary Outcome Measures. 
Objective cognitive performance will be measured by the psychomotor vigilance task (PVT), a simple 
reaction time task with outcome measures including mean reaction time, response speed (1/reaction 
time) and number of lapses (reaction time >500 ms). PVT performance will be measured at, or near, the 
timing of top of descent (TOD) during each flight. 
Statistical Analyses.  
 
The following factors will be also considered for inclusion in the analysis: 
• 
Schedule features: flight duration, duty duration, duty start and finish times 
• 
Individual factors: age, experience, chronotype (as measured by the morningness-eveningness 
questionnaire), sleep need 
• 
Sleep: sleep duration, sleep loss, sleep start and finish times (all measured by the actiwatch) 
• 
Fatigue/alertness: pre- and post-sleep and on-duty fatigue and alertness ratings (as measured 
by subjective scales) 
• 
Workload: hassle factors encountered during flights and NASA TLX 
 
8.2 Equipment  
 
The study will involve evaluating pilot sleep, sleepiness, performance, and workload among on-duty 
pilots. All devices are commercial, off-the-shelf products with no modifications and used as directed.  
iPod. Participants will be issued an iPod Touch with a pre-loaded application (NASA PVT+) which 
includes a sleep diary, cognitive tests, and subjective scales (Figure 1). Using the NASA PVT+ App, 
measures will include PVT speed (1/reaction time) and lapses conducted at pre-flight, top of descent 
(TOD), post-flight, and on days off. Subjective fatigue ratings using the Samn-Perelli 7-point scale and 
sleepiness ratings using the 9-point Karolinska Sleepiness Scale at pre-flight, TOD, post-flight, and on 
days off will also be reported. At the end of each flight, participants will complete the NASA-TLX, hassle 
factors, and information about any fatigue countermeasures that they used. They will also capture 
information about the characteristics of the flight at the end of each Flight Duty Period (FDP). Prior to 
and at the end of the study, they will use the app to complete baseline questionnaires.   
Actigraphy. Participants will wear a small wristwatch-like device (Actiwatch, Philips Respironics, 
Murrysville, PA, USA) on the wrist of their non-dominant arm (Figure 2). The actiwatch will be worn 
continuously throughout the study period including on days off. Actigraphy uses accelerometry and a 
light sensor to determine sleep and wake patterns and may be worn for several weeks at a time. It will 
provide us with objective sleep measures which can be compared and correlated with other measures 
recorded in the NASA PVT+ App. 

Light and Temperature Sensor. Participants will wear a small (~1 square inch) light sensor clipped to 
their clothing in order to assess their lighting and ambient temperature exposure. This device can be 
placed on a bedside table during sleep. It can record light information for several weeks and does not 
require the user to interact with it in any way. The data obtained from this sensor will allow us to use 
the participant’s pattern of light exposure to estimate circadian phase using a biomathematical model 
(Mohamed et al., 2021).    
 
 
Figure 1. NASA PVT+ App screenshots 
 
 
 

 
Figure 2. Actiwatch Spectrum Device 
 
8.3 Stimuli 
None 
8.4 Prior to Runs 
Recruitment material will be disseminated via company email and safety newsletters.  
Interested participants will be asked to contact a research coordinator to confirm their interest and 
eligibility. If the participant is interested and eligible, the research coordinator will send a copy of the 
consent form via email for the participant to review and then schedule a time at least 24 hours later for 
a designated member of the research team to review the informed consent and study procedures with 
the participant. Informed consent will be completed by the principal investigator or a designated 
member of the study staff. As pilots could be based in many locations across the country, informed 
consent will be completed either by phone, video conference, or in person.  If the informed consent 
session is not conducted in-person, DocuSign will be used to obtain the participant’s signature and an 
electronic copy of the signed consent will be emailed to the participant. If the informed consent session 
is conducted in-person, a paper copy with wet ink signature may be collected and a photocopy will be 
given to the participant.  
8.5 Experiment Design 
We will collect objective and subjective sleep, sleepiness, workload, and performance data from on-duty 
pilots during the aforementioned short-haul flight operations. Data will be collected during days off prior 
to the trip start, during flights, and during days off following the flight operations. Each pilot will collect 
data during at least two trips. 

8.6 Data Protection 
Types of Data. Several questionnaires and PVT tests will be collected using the iPod app. All of the 
questionnaires are included in the supplemental material submitted with this protocol. We will not 
collect any personally identifying information using the app. We will collect the participant’s name, e-
mail address, phone number, and preferred mailing address solely for the purposes of conducting the 
study (i.e., to coordinate mailing the study devices and to provide compensation, if applicable).   
Data Management/Storage. To ensure that individual crew data remains confidential, participants will 
be allocated an individual numerical code. All data will be collected using this code and not the 
individual’s name or other identifiable information. The data sheet linking names and codes will be 
stored on an encrypted hard drive following NASA IT security rules.  
Coded study data will be stored on devices provided by each airline and/or their research partner (Delta 
Airlines partners with Dr. Barger at Brigham and Women’s Hospital; United Airlines partners with Dr. 
Lamp at Washington State University). Coded data from all airlines will be archived and aggregated at 
Washington State University for processing and analysis. Data access will be limited to personnel named 
on this protocol. NASA researchers will access study data either via computers provided by the airlines 
or their research partners or via encrypted VPN. The results of the research will not be presented in any 
form that identifies individuals. 
The data will not be used to make employment measures or decisions with respect to individuals.  
Participant Withdrawal. Participants who choose to withdraw their consent may do so at any time. Any 
partial data that has been collected will be considered for analysis unless the participant requests that 
their data be deleted. 
9. Proposed Test Schedule  
The study will take place over an estimated one-year period. Each participant will collect data during 
two trips lasting 2-7 days each, with up to 3 days of off-duty data collection before and after each trip, 
for a total data collection of up to 26 days per pilot. 
Pre-study Questionnaires 
Once consented, participants will be provided with instructions regarding the study procedures and 
equipment (i.e., an iPod with the NASA PVT+ application, an Actiwatch, and a light and temperature 
sensor). Equipment will be either be mailed to the participant or available for collection from a 
designated staff member. Participants will then complete a series of baseline questionnaires including a 
demographic questionnaire, performance questionnaires, a baseline exercise questionnaire, the 
Morningness/Eveningness Questionnaire (MEQ), the Epworth Sleepiness Scale (ESS), the Pittsburgh 
Sleep Quality Index (PSQI), the Insomnia Severity Index (ISI), and the NASA Task Load Index (TLX), using 
the NASA PVT+ app. Participants will also complete a practice sleep diary and a practice PVT in order to 
ensure that they understand the study procedures. Demographic information, including age, flight 
experience, living arrangements, and the results of the aforementioned questionnaires will be used as 
covariates in data analysis as each of these factors can influence sleep and performance. 
Procedure 

Participants will begin data collection 1-3 days prior to their trip departure (depending on the 
participant’s availability and off-duty time between trips). Data will be collected using the NASA PVT+ 
App and the Actiwatch. Participants will begin wearing the Actiwatch and continue to wear it for the 
duration of the study period which will conclude up to 3 days following their return from their trip. They 
will make entries in the App reporting on their sleep periods at the beginning and end of each day, 
including days off. Participants will also have additional entries during flight duty periods.  
A study staff member will check in (e.g., via phone call) regularly to remind the participant to complete 
the study tasks and to answer any additional questions. 
 Details are outlined below as well as summarized in Table 2 and Figure 3. Full details can be found in 
supplemental documents. 
Return of equipment. Participants will be provided with either a return pre-paid box or instructions on 
where to return the equipment to a designated staff member. Data will be downloaded, cleared, and a 
study ID reset on each device before sending to another participant. Data collected on iPod and 
actiwatch devices will only be identified by an ID code. No identifying information will be collected 
during the study period. 
 
Morning Sleep Diary. At the beginning of each day, participants will complete a sleep diary within the 
NASA PVT+ App. Each entry will include: wake-up time, a rating of sleep quality (5 -point scale from 
Extremely Good to Extremely Poor), the Samn-Perelli (SP) and Karolinska Sleepiness Scale (KSS), the 
location of their sleep, the timing and duration of any awakenings during the sleep period, and any 
additional information (i.e., notes).   
Evening Sleep Diary. At the end of each day (right before sleep), participants will use the App to report 
the time they are going to sleep, the location of their sleep (e.g., home, hotel), if they used any caffeine 
during the day (amount used), any naps during the day (including timing and duration), timing/type of 
meals, and timing/type of exercise. Participants will also complete the SP and KSS and have an 
opportunity to provide any additional information about the day if necessary. 
Flight Duty Period Data Collection. On flight duty days, participants will have additional entries and 
tasks to complete within the NASA PVT+ App (i.e., pre-duty, during flight, post-flight, and post-duty). 
Pre-duty entries will include: flight information, layover information, commute information, caffeine 
intake, the SP and KSS, and the Psychomotor Vigilance Task (PVT). During their flight, they will complete 
the SP, KSS, and the PVT, at or near the timing of TOD. Post-flight entries will occur within one hour of 
landing and will include flight information, the NASA TLX, report of fatigue countermeasures used, and 
hassle factors experienced (e.g., weather, air traffic control issues, traffic), SP, KSS, and PVT (if needed). 
Post-duty entries will include: duty information, operational factors (e.g., delays, sit times), overall 
fatigue rating (visual analog scale), KSS, SP, and PVT. Participants will also complete both the morning 
and evening sleep diary entries on flight duty days. Additional questions in the evening sleep diary on 
duty days include: commute information (i.e., timing, duration, and type of travel). 
 

Table 2. Timing of data collection (repeated for one circadian-disruption trip and one trip without 
circadian disruption) 
 
1-3 Off-duty Days 
Each Day of the Trip 
1-3 Off-duty Days 
Morn/evening 
Sleep Diary 
✓ 
✓ 
✓ 
Sleepiness/ 
Fatigue 
✓ 
✓ 
✓ 
Performance 
✓ 
✓ 
✓ 
Workload 
 
✓ 
 
Duty information 
 
✓ 
 
 
 
Figure 3. Timing of flight day data collection 
 
Tests and Scales 
Morningness/Eveningness Questionnaire (MEQ). The MEQ is a widely used self-assessment 
questionnaire (19 items) designed to determine a person’s chronotype, that is, whether they experience 
peak alertness in the morning, evening, or in between. 
Pittsburgh Sleep Quality Index (PSQI). The PSQI is used to measure sleep quality in adults over the last 
month. The scale is broken down into 7 Components, which include: subjective sleep quality, sleep 
latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medications, and 
daytime dysfunction. Higher scores indicate poorer sleep quality. 
Upon 
waking
Pre-
Duty
At/near 
Top of 
Descent 
(TOD)
Post-
flight
Post-
duty
Before 
bed

Insomnia Severity Index (ISI). The ISI is a 7-item questionnaire used to assess the severity of daytime 
and nighttime components of insomnia. The scale uses a 5-point Likert scale to measure the different 
components, including: severity sleep onset, sleep maintenance, early morning awakening problems, 
sleep dissatisfaction, interference of sleep difficulties with daytime function, noticeability of sleep 
problems by others, and distress caused by the sleep difficulties. Total score can range from 0-28 with 
higher scores indicating more severe insomnia. 
Epworth Sleepiness Scale (ESS). The ESS is a routinely used self-administered questionnaire (8 items) 
that can be used to assess daytime sleepiness. 
NASA-TLX. The NASA Task Load Index (TLX) is a subjective, multidimensional tool that rates workload 
relative to a task. The TLX is taken at the start of the study to make a series of pairwise comparisons and 
then again for rating each flight period.  
Hassle Factors. Factors that may affect workload during flight operations (e.g., weather, air traffic 
control (ATC), cabin activity, procedures & documentation) will be reported for each flight period. 
Samn-Perelli Scale (SP). The Samn-Perelli Scale is a commonly used 7-point scale for self-rating levels of 
fatigue at a given time. The scale includes: 1= fully alert – wide awake, 2= very lively, 3= okay - 
somewhat fresh, 4= a little tired, 5= moderately tired, 6= extremely tired, 7= completely exhausted. 
Karolinska Sleepiness Scale (KSS). The KSS is a widely used 9-point scale for self-rating levels of 
sleepiness at a given time. The scale includes: 1 = extremely alert, 2= very alert, 3 = alert, 4= rather alert, 
5 = neither alert nor sleepy, 6= some signs of sleepiness, 7 = sleepy – but no difficulty remaining awake, 
8= sleepy – some effort to keep awake, and 9 = extremely sleepy – fighting sleep.  
Sleep Quality rating. All sleep periods (including naps) will be rated for quality. The scale includes: 1 = 
extremely good, 2= good, 3 = average, 4= poor, 5 = extremely poor. 
Psychomotor vigilance task (PVT). The PVT is a widely used sustained-attention, reaction-time task that 
measures the speed with which subjects respond to a visual stimulus. The PVT is a simple task where the 
subject taps the screen as soon as a visual stimulus appears. The stimulus appears randomly every few 
seconds during the 5-minute task.  
The initial screen orients the subject to take the test in landscape mode with thumbs hovering over the 
screen for response (Figure 4). 

 
Figure 4. Orientation screen shown prior to each PVT  
At random intervals the counter starts running with the clock showing in the response box (Figure 5). 
Tapping the screen stops the counter, showing the reaction time, before the screen clears and readies 
for the next stimulus presentation. At the end of the test the screen will display DONE. 
 
Figure 5. PVT screen showing response time (ms) 
 
10. Practical Aspects of Safety and Ethical Conduct  
 

This study is a minimal risk study. The risks associated with the protocol may differ from normal flying 
duties due to potential discomfort and inconvenience with wearing the actiwatch and completing tests 
with the PVT+ App. All participants are active-duty pilots with the appropriate clearances for flight 
duties. The actiwatch and iPod device housing the NASA PVT+ App are commercially available products. 
Participants will be informed that they may skip tests or stop the study at any time if they feel that their 
participation compromises flight safety. Given that the risks associated with this study are minimal, 
medical monitoring is not required.  
11. Number, Source, and Pertinent Characteristics of Participants  
Study Population. The study population does not include astronauts. All subjects will be medically 
qualified, active-duty flight crewmembers. Current American Airlines, United Airlines, Delta Airlines, and 
Southwest Airline pilots are eligible to participate in the study (pending review of other inclusion 
criteria, see below). 
Participant Recruitment. Members of fatigue risk management teams and union representatives across 
each airline will distribute recruitment material via e-mail and in safety newsletters to short-haul flight 
crew. When feasible, members of the study team may set up study information tables in the crew rooms 
at airports.  Participation will be completely voluntary.  
Participants will not be excluded based on race, ethnicity, or gender. 
Sample Size. Based on previous studies in similar studies of chronic sleep loss compared to 
rested performance, we expect that the effect size for PVT lapses using a 5-minute PVT will be 
approximately 0.75. When accounting for the clustered nature of the study (i.e., four airlines), 
we estimate the inter-class correlation adjustment to be .015. As such, with an alpha level of 
0.05 and 80% power, we estimate that we need 18 participants per condition (night flying or 
circadian switches), per airline for a total sample size of 36 participants per airline. In order to 
account for attrition after consent, unplanned schedule changes, and incomplete data 
collection, we would like to recruit up to an additional 15 participants per airline. This would 
result in a total sample size of 204 pilots.    
Inclusion/Exclusion Criteria. All medically qualified, active-duty pilots currently flying short-haul 
operations are eligible to be included as participants in the study. Participants must be line pilots that 
spend at least 50% of their typical monthly schedule flying short-haul operations (defined at flights 
under 6 hours duration). 
All flight crew who fly short-haul operations that meet the following study inclusion criteria will be 
eligible for participation. 
Participants must be scheduled for and willing to collect data on each of the following: 
a.  Trip with Circadian Disruption: A trip containing one of the following types of WOCL 
infringement: 

i. Overnight FDPs. An FDP in which the pilot is operating one or more flights 
through the WOCL (0200-0559h) relative to the pilot’s home-base time or clock 
time. 
OR 
ii. Circadian Switching. At least one FDP that starts between 0000-0659h relative 
to home-base time, followed by at least one FDP that ends between 0000-
0659h, or vice versa, within the same trip (e.g., an FDP that begins at 0500h and 
the next FDP ends at 0100h or vice versa). 
AND 
b. Trip without Circadian Disruption: This trip must not contain any duties that are scheduled 
to begin or end between 0000h and 0659h relative to home-base time. 
Proposed Test Schedule. Pending final decisions by the airlines regarding flights to be studied, the study 
is expected to commence in the summer of 2022. 
 
12. Benefits of Participation 
The results of this study may inform our understanding of how fatigue emerges during typical short-haul 
operations in the United States.  
13. Possible Inconveniences, Discomfort, Pain, and Risks to the Participants  
The risks associated with the protocol may differ from normal flying duties as follows:  
It is possible that crew could experience slight discomfort and inconvenience from wearing an Actiwatch 
such as skin irritation or a rash, although no more than from wearing a wristwatch.  An Actiwatch is the 
size of a wristwatch and is designed to be worn for weeks at a time.  
Participants will record their performance using a handheld device employing the data collection app. 
Some crew could experience a degree of discomfort and inconvenience as the result of having their 
performance recorded for an extended period. Participants could be distracted from their flight duties 
while taking the tests, however, they will be instructed to take the test prior to the TOD, while still in the 
cruise phase when distractions are minimal.  
Participants may also be inconvenienced by having to complete sleep, fatigue, and workload ratings. 
However, it is estimated that study information will only take about a total of 30 min in a day to record, 
with each phase of collection (e.g., pre-duty, evening diary) taking no more than 7 minutes. 
As the study data will be archived at each airline or airline partner, it is possible that individual ID-coded 
data could be viewed or used by airline personnel.  
14. Measures Taken to Minimize Discomfort and Risks  

If the participant finds the actiwatch uncomfortable, then the study staff will work with the participant 
to determine if a different band could be used to minimize discomfort. If no acceptable alternatives are 
identified, then the participant will be free to discontinue wearing the device, which may require 
withdrawal from the study. 
Participants will also be instructed to stop taking the PVT if they need to attend to their flying duties. 
Participants will be informed that they are free to withdraw from the study at any time if they find the 
daily sleep logs and questionnaires too burdensome. 
Participants will be informed that their coded data will be stored at their airline and at Washington State 
University. Only coded data will be archived with each airline in order to minimize the possibility that an 
individual’s name could be linked to their data. 
15. Conditions of Withdrawal from the Experiment 
Participation is voluntary and pilots may choose not to participate in all or part of the study and can 
withdraw at any stage without being penalized or disadvantaged in any way. 
16. Remuneration for Participants  
All participants will be provided with NASA stickers, patches, mugs, or similar items as a token of 
appreciation for participation.  
Compensation will be provided to participants according to the established rate for similar studies at 
each airline (if any). 
17. Compensation in the Event of Injury  
In the event of injury or illness resulting from this study and calling for immediate action or attention, 
NASA will provide, or cause to be provided, the necessary treatment. If eligible for California Workers’ 
Compensation benefits while participating in this study, participants cannot sue their employer because 
the law makes Workers’ Compensation their only remedy against their employer. Participants may have 
other remedies against other persons or organizations, depending on the circumstances of the injury. 
NASA will pay for any claims of injury, loss of life or property damage to the extent required by Federal 
Employees Compensation Act or the Federal Tort Claims Act. 
Insurance or medical support that is normally provided to all air crew under company policy provisions 
at each airline will apply for study participants. 
18. Consent Process 
Members of fatigue risk management teams and union representatives across each airline will distribute 
recruitment material via e-mail and in safety newsletters to short-haul flight crew. When feasible, 
members of the study team may set up study information tables in the crew rooms at airports.  
Participation will be completely voluntary. 

Interested participants will be asked to contact a research coordinator to confirm their interest and 
eligibility. If the participant is interested and eligible, the research coordinator will send a copy of the 
consent form via email for the participant to review and then schedule a time at least 24 hours later for 
a designated member of the research team to review the informed consent and study procedures with 
the participant. Informed consent will be completed by the principal investigator or a designated 
member of the study staff. As pilots could be based in many locations across the country, informed 
consent will be completed either by phone, video conference, or in person.  If the informed consent 
session is not conducted in-person, DocuSign will be used to obtain the participant’s signature and an 
electronic copy of the signed consent will be emailed to the participant. If the informed consent session 
is conducted in-person, a paper copy with wet ink signature may be collected and a photocopy will be 
given to the participant.  
Participants may choose to withdraw from the study at any stage without being penalized or 
disadvantaged in any way. Participants will be told to contact the study staff if they wish to withdraw 
from the study. The study staff will make arrangements to collect the study equipment from the 
participant at their earliest convenience.  
 
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