a

GAO

United States Government Accountability Office

Report to the Chairman, Subcommittee 

on Aviation, Committee on 

Transportation and Infrastructure, House 

of Representatives

November 2004 AIR TRAFFIC 

CONTROL

FAA Needs to Ensure 

Better Coordination 

When Approving Air 

Traffic Control 

Systems

GAO-05-11
www.gao.gov/cgi-bin/getrpt?GAO-05-11.

To view the full product, including the scope 

and methodology, click on the link above. 

For more information, contact Katherine 

Siggerud at (202) 512-2834 or 

siggerudk@gao.gov. 

Highlights of GAO-05-11, a report to the 

Chairman, House Aviation Subcommittee, 

Committee on Transportation and 

Infrastructure 

November 2004

AIR TRAFFIC CONTROL 

FAA Needs to Ensure Better Coordination 

When Approving Air Traffic Control 

Systems 

The Federal Aviation 

Administration’s (FAA) process for 

ensuring that air traffic control 

(ATC) systems will operate safely 

in the national airspace system is 

an integral part of the agency’s 

multibillion-dollar ATC 

modernization and safety effort. 

GAO was asked to review (1) FAA’s 

process for approving ATC systems 

for safe use in the national airspace 

system; (2) challenges FAA has 

faced approving ATC systems and 

how these challenges affected the 

cost, schedule, and performance 

estimates of the systems; and (3) 

actions FAA has taken to improve 

its process for approving ATC 

systems. 

GAO is recommending that FAA 

develop ATC system-specific plans 

early in the approval process that 

specify how and when the 

approving and certifying offices 

within FAA and other stakeholders, 

including controllers, maintenance 

technicians, technical experts, and 

industry representatives, will meet 

to ensure coordination. FAA 

generally agreed with the findings 

and recommendation in this report. 

FAA has separate processes for approving ground systems and certifying 

aircraft equipment for safe use in the national airspace system. FAA’s 

process for approving ground systems, such as radar systems, is done in 

accordance with policies and procedures in FAA’s Acquisition Management 

System. Approving ground systems, which are usually developed, owned, 

and operated by FAA, typically involves FAA’s Air Traffic Organization 

determining whether a vendor is in compliance with contract requirements, 

followed by a rigorous test-and-evaluation process to ensure that the new 

system will operate safely in the national airspace system. The process for 

certifying aircraft equipment, which is usually developed by private 

companies, is done in accordance with Federal Aviation Regulations, with 

FAA serving as the regulator. If a system has both ground components and 

aircraft equipment components, then the system must go through both 

processes before it is approved for safe use in the national airspace system. 

FAA has faced challenges approving systems for safe use in the national 

airspace system that contributed to cost growth, delays, and performance 

shortfalls in deploying these systems. We identified three specific challenges 

through the review of 5 ATC systems and our past work. These challenges 

are the need to (1) involve appropriate stakeholders, such as users and 

technical experts, throughout the approval process; (2) ensure that the FAA 

offices that have responsibility for approving ground systems and certifying 

aircraft equipment effectively coordinate their efforts for integrated systems; 

and (3) accurately estimate the amount of time needed to meet complex 

technical requirements at the beginning of the design and development 

phase. 

FAA has taken some actions to address two of the three challenges we 

identified. However, FAA has not taken action to fully involve all 

stakeholders, such as air traffic controllers and technical experts, 

throughout the approval process. FAA officials believe that the agency’s new 

Safety Management System will help ensure that the ground system approval 

and aircraft certification processes are better coordinated. FAA stated that 

coordination would improve because, as part of the new Safety Management 

System, the agency plans to realign its organizational structure to create a 

formal link between the Air Traffic Organization and the Office of Regulation 

and Certification. FAA expects full implementation of this system to take 3 

to 5 years. We are reserving judgment on whether this change will fully 

address the challenge because of the early state of this effort and FAA’s longstanding problems with internal coordination when approving ATC systems. 

As such, we believe that FAA should, in the interim, develop specific plans 

that describe how both internal and external coordination will occur on a 

system-specific basis. 
Page i GAO-05-11 Air Traffic Control

Contents

Letter 1

Results in Brief 3

Background 6

FAA Has Separate Processes for Approving Ground Systems and 

Certifying Aircraft Equipment 11

FAA Faced Challenges in Approving Several ATC Systems 16

FAA Has Taken Action to Improve Its Process for Approving ATC 

Systems 23

Conclusions 26

Recommendation for Executive Action 27

Agency Comments 28

Appendixes

Appendix I: Objectives, Scope, and Methodology 29

Appendix II: Airport Surface Detection Equipment - Model X Case 

Illustration 31

Background 31

Status 32

FAA Faced Fewer Challenges in Approving ASDE-X 33

Appendix III: Controller-Pilot Data Link Communications Case 

Illustration 35

Background 35

Status 36

Challenges in Approving CPDLC 37

Appendix IV: Local Area Augmentation System Case Illustration 40

Background 40

Status 41

FAA Faced Challenges in Approving LAAS 42

Certification of LAAS Aircraft Equipment Has Been Affected by 

Delays in Ground System Approval 44

FAA’s Aircraft Certification Office Needs to Coordinate Better with 

Acquisition Offices 45

Appendix V: Standard Terminal Automation Replacement System Case 

Illustration 46

Background 46

Status 47

FAA Faced Challenges in Approving STARS 47

Appendix VI: Wide Area Augmentation System Case Illustration 50
Contents

Page ii GAO-05-11 Air Traffic Control

Background 50

Status 51

FAA Faced Challenges in Approving WAAS 52

FAA Did Not Experience Major Challenges in Certifying the Aircraft 

Equipment of WAAS 54

Appendix VII: GAO Contacts and Staff Acknowledgments 56

GAO Contacts 56

Staff Acknowledgments 56

Tables Table 1: FAA Systems Used as Case Illustrations 10

Table 2: Cost and Schedule Estimate Changes to ASDE-X 33

Table 3: ASDE-X Ground System Approval Timeline 34

Table 4: Cost and Schedule Estimate Changes to CPDLC 37

Table 5: CPDLC Ground System Approval Timeline (Build 1) 38

Table 6: CPDLC Ground System Approval Timeline (Build 1A) 38

Table 7: CPDLC Aircraft Equipment Certification Timeline 39

Table 8: Cost and Schedule Estimate Changes to LAAS 42

Table 9: LAAS Ground System Approval Timeline 44

Table 10: LAAS Aircraft Equipment Certification Timeline 45

Table 11: Cost and Schedule Estimate Changes to STARS 47

Table 12: STARS Ground System Approval Timeline 49

Table 13: Cost and Schedule Baseline Changes to WAAS 52

Table 14: WAAS Ground System Approval Timeline 54

Table 15: WAAS Aircraft Equipment Certification Timeline 55

Figures Figure 1: Current FAA Offices with Responsibility for Approving 

Air Traffic Control Systems 7

Figure 2: Airport Surface Detection Equipment - Model X 32

Figure 3: Controller-Pilot Data Link Communications 36

Figure 4: LAAS Infrastructure 41

Figure 5: Standard Terminal Automation Replacement System 46

Figure 6: WAAS Architecture 50
Contents

Page iii GAO-05-11 Air Traffic Control

Abbreviations

ASDE-X Airport Surface Detection Equipment - Model X

ATC air traffic control

CPDLC Controller-Pilot Data Link Communications

DOD Department of Defense

FAA Federal Aviation Administration

GPS Global Positioning System

LAAS Local Area Augmentation System

STARS Standard Terminal Automation Replacement System

WAAS Wide Area Augmentation System

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Page 1 GAO-05-11 Air Traffic Control

United States Government Accountability Office

Washington, D.C. 20548

A

November 17, 2004 Letr

The Honorable John L. Mica

Chairman, Subcommittee on Aviation

Committee on Transportation and Infrastructure

House of Representatives

Dear Mr. Chairman:

The Federal Aviation Administration’s (FAA) process for ensuring that air 

traffic control systems will operate safely in the national airspace system is 

an integral part of FAA’s multibillion-dollar air traffic control modernization 

and safety effort. New air traffic control systems cannot be used in the 

national airspace system until FAA has determined that the systems will 

operate safely. Over the years, FAA has approved about 45,000 pieces of air 

traffic control equipment for safe use in the national airspace system. Some 

in the aviation industry and government contend that FAA’s approval 

process for air traffic control systems is too lengthy and, therefore, 

contributes to cost growth, schedule delays, and performance problems 

that have plagued many of the systems that FAA has been trying to develop 

for years. In addition, some in the aviation industry have raised concerns 

about whether FAA’s approval process has kept pace with changes in 

technology. For example, more of today’s new air traffic control systems 

are integrated—that is, involving both ground systems1

 and equipment used 

exclusively in aircraft (aircraft equipment) that must work together—than 

in the past.

In response to your request, we examined 

• FAA’s process for approving air traffic control systems for safe use in the 

national airspace system; 

• challenges FAA faces in approving air traffic control systems and how 

these challenges have affected the cost, schedule, and performance of 

the systems; and 

1

Ground systems are air navigation facilities that, among other things, aid in the guiding or 

controlling of flight, including the landing and takeoff of aircraft. For the purposes of this 

report, ground systems include the satellites that may be associated with them.
Page 2 GAO-05-11 Air Traffic Control

• actions FAA has taken to improve its process for approving air traffic 

control systems.

In this report, we use the word “approval” to describe the process of 

ensuring the safety of an air traffic control system when it has both a 

ground system and aircraft equipment. We also use the word “approval” to 

describe the process of ensuring the safety of ground systems exclusively. 

We use the word “certification” to describe the process of ensuring the 

safety of aircraft equipment for safe use in the national airspace system. 

To identify FAA’s process for approving air traffic control systems for safe 

use in the national airspace system, we reviewed FAA documents that 

describe the agency’s process for approving such systems and equipment 

and RTCA’s 1999 and 2001 reports that also address this process.2

 To 

determine the challenges FAA has faced in approving air traffic control 

systems and how these challenges affected the cost, schedule, and 

performance of the systems, we (1) conducted case illustrations on 5 of 

FAA’s 25 air traffic control systems currently receiving funding that were 

approved or in the process of being approved for safe use in the national 

airspace system and (2) reviewed reports prepared by GAO and the 

Department of Transportation’s Inspector General. The 5 air traffic control 

systems are 

• Airport Surface Detection Equipment - Model X (ASDE-X),

• Controller-Pilot Data Link Communications (CPDLC),

• Local Area Augmentation System (LAAS),

• Standard Terminal Automation Replacement System (STARS), and

• Wide Area Augmentation System (WAAS).

2

Organized in 1935 and once called the Radio Technical Commission for Aeronautics, RTCA 

is today known just by its acronym. RTCA is a private, not-for-profit corporation that 

develops consensus-based performance standards for air traffic control systems. RTCA 

serves as a federal advisory committee and its recommendations are the basis for a number 

of FAA’s policy, program, and regulatory decisions. In 1999, RTCA published its Final Report 

of the Task Force 4: Certification. In 2001, RTCA published RTCA Task Force 4 – 

Certification Implementation Plans and Responsibilities.
Page 3 GAO-05-11 Air Traffic Control

We selected these 5 systems because collectively they accounted for about 

46 percent of FAA’s air traffic control modernization costs in fiscal year 

2002 and 3 of the 5 systems are integrated—that is, they require the 

approval of the ground systems as well as certification of aircraft 

equipment before they can be used in the national airspace system. In 

addition, we interviewed, among others, officials from FAA program 

offices; RTCA; aviation industry groups; manufacturers of aircraft 

equipment; ground system developers, including Honeywell, Raytheon, and 

Sensis Corporation; industry experts; Wide Area Augmentation System 

Integrity Performance Panel3

 and Local Area Augmentation System 

Integrity Panel members;4 and unions representing air traffic controllers 

and maintenance technicians. We also reviewed reports on air traffic 

control systems prepared by GAO, the Department of Transportation’s 

Inspector General, RTCA, and the Commission on the Future of the U.S. 

Aerospace Industry (Aerospace Commission). To identify what actions 

FAA has taken to improve its processes for approving air traffic control 

systems, we interviewed representatives from FAA, RTCA, the Aerospace 

Commission, and aviation industry groups. See appendix I for additional 

information on our objectives, scope, and methodology. We conducted our 

review from October 2003 through September 2004 in accordance with 

generally accepted government auditing standards. 

Results in Brief FAA has separate processes for approving ground systems and certifying 

aircraft equipment for safe use in the national airspace system. FAA’s 

process for approving ground systems, such as radar systems, is done in 

accordance with policies and procedures in FAA’s Acquisition Management 

System. The process to approve ground systems, which are usually 

developed, owned, and operated by FAA, involves FAA’s Air Traffic 

3

The Wide Area Augmentation System Integrity Performance Panel is a team of satellite 

navigation specialists formed in January 2000 to help FAA meet Wide Area Augmentation 

System’s integrity requirement to alert the pilot in a timely manner when it should not be 

used. FAA’s integrity requirement stipulates that the Wide Area Augmentation System 

cannot fail to warn pilots of misleading information that could potentially create hazardous 

situations more than once in 10 million approaches.

4

The Local Area Augmentation System Integrity Panel is a team of satellite navigation 

specialists formed in 1996 but formally tasked in 2003 to help FAA meet the Local Area 

Augmentation System’s requirement to alert the pilot in a timely manner when it should not 

be used. FAA’s integrity requirement stipulates that the Local Area Augmentation System 

cannot fail to warn pilots of misleading information that could potentially create hazardous 

situations more than once in 10 million approaches.
Page 4 GAO-05-11 Air Traffic Control

Organization determining whether a vendor is in compliance with contract 

requirements and/or FAA operational requirements, followed by a rigorous 

test-and-evaluation process to ensure that the new system will operate 

safely in the national airspace system. In contrast, federal aviation law 

requires that aircraft equipment, which is usually developed by private 

companies, be certified in accordance with Federal Aviation Regulations, 

with FAA serving as the regulator. Unlike the approval of ground systems, 

which FAA accomplishes with the help of a contractor, FAA is not typically 

involved in the development of the equipment. An applicant, such as a 

manufacturer of aircraft equipment, generally brings fully developed 

aircraft equipment to FAA for certification. If an air traffic control system 

has both a ground system and aircraft equipment, as was the case for 3 of 

the 5 systems we reviewed, then the system must go through both 

processes before it is approved for safe use in the national airspace system.

FAA has faced challenges in approving air traffic control systems for safe 

use in the national airspace system. This report focuses on three specific 

challenges we identified through our past work and our case illustrations of 

5 air traffic control systems. Most of these challenges have made it more 

difficult for FAA to meet the systems’ cost, schedule, or performance 

estimates. These challenges are as follows: 

• Involving appropriate stakeholders, such as users and technical 

experts, throughout the ground system approval process. For example, 

during the design and development phase of the Standard Terminal 

Automation Replacement System, which is designed to replace air 

traffic controller workstations with new color displays, FAA did not 

involve users such as air traffic controllers and maintenance technicians 

in human factor evaluations, which examine how humans interact with 

machines, because the aggressive development schedule limited the 

amount of time available to involve them. Consequently, FAA and the 

contractor later had to restructure the contract to address the 

controllers’ and technicians’ concerns, such as the inconsistency of 

visual warning alarms and color codes, which contributed to the system 

being delayed by 3 years and a cost increase of $500 million.

• Ensuring that the FAA offices that have responsibility for approving 

ground systems and certifying aircraft equipment effectively 

coordinate their efforts for integrated systems. For example, although 

the Wide Area Augmentation System was being developed by an 

integrated product team that included representatives from various FAA 

offices, the team did not function effectively in resolving issues related 
Page 5 GAO-05-11 Air Traffic Control

to meeting an important functional requirement to alert the pilot in a 

timely manner when the system should not be used because of a 

possible error. According to FAA officials, the reason coordination was 

not effective was because the two offices had competing priorities that 

were not associated with development of the Wide Area Augmentation 

System. This ineffective coordination, combined with other factors,

contributed to a 6-year delay in commissioning the Wide Area 

Augmentation System and a $1.5 billion increase in its development 

costs. 

• Accurately estimating the amount of time needed to meet complex 

requirements at the beginning of the design and development phase.

For example, FAA accelerated the schedule for the Standard Terminal 

Automation Replacement System in 1995. This acceleration in schedule 

left only limited time for human factor evaluations and, according to 

FAA officials, added $500 million to the Standard Terminal Automation 

Replacement System’s cost and 3 years to the schedule because the 

agency had to revise its strategy for acquiring and approving it. 

FAA has taken actions to address two of the three challenges we identified. 

However, FAA has not taken action to fully involve all stakeholders, such as 

air traffic controllers, maintenance technicians, technical experts, and 

industry representatives, throughout the approval process. To ensure that 

the two offices effectively coordinate their ground system approval and 

aircraft equipment certification processes, FAA officials believe that the 

agency’s new Safety Management System, which is designed to formalize 

and standardize the agency’s safety process, will improve overall 

coordination among FAA stakeholders once the system is implemented. 

FAA stated that coordination would improve because, as part of the new 

Safety Management System, the agency plans to realign its organizational 

structure to create a formal link between the Air Traffic Organization, 

which currently approves ground systems, and the Office of Regulation and 

Certification. FAA expects full implementation of this system to take 3 to 5 

years. We are reserving judgment on whether this change will fully address 

the challenge because of the early state of this effort and because FAA’s 

problems with internal coordination when approving air traffic control 

systems are long-standing. In addition, because FAA has historically faced 

internal and external coordination challenges in approving air traffic 

control systems for safe use in the national airspace system, we believe 

that as FAA moves forward with implementing the agency’s new Safety 

Management System, it should, in the interim, develop plans that describe
Page 6 GAO-05-11 Air Traffic Control

how both internal and external coordination will occur on a systemspecific basis. In addition, plans to include external stakeholders are 

particularly important since the Safety Management System is not intended 

to address this challenge.

We are recommending that FAA develop early in the approval process air 

traffic control system-specific plans that specify how and when the 

approving and certifying offices within FAA and other stakeholders, 

including controllers, maintenance technicians, technical experts, and 

industry representatives, will meet to ensure coordination.

Background Several offices within FAA’s Air Traffic Organization and Office of 

Regulation and Certification have responsibility for approving ground 

systems and certifying aircraft equipment, as shown in figure 1. 
Page 7 GAO-05-11 Air Traffic Control

Figure 1: Current FAA Offices with Responsibility for Approving Air Traffic Control 

Systems

Note: The Office of Regulation and Certification’s Air Traffic Safety Oversight Service oversees and 

collaborates with the Air Traffic Organization’s Safety Services on the safety of air traffic control 

systems.

Before the creation of the Air Traffic Organization in November 2003, FAA’s 

Research and Acquisitions (acquisitions office) and Air Traffic Services 

FAA Administrator

Office of Regulation and

Certification

Air Traffic Organization

Safety

Services

Source: FAA.

Flight Standards

Service

Aircraft Certification

Service

Air Traffic Safety

Oversight Service

En Route and 

Oceanic

Services

Terminal

Services

Flight

Services

System

Operations

Services

Technical

Operations

Services
Page 8 GAO-05-11 Air Traffic Control

were the primary offices responsible for approving ground systems for safe 

use in the national airspace system. The 5 systems that we reviewed began 

the approval process under that structure. Currently, these offices, 

although renamed, form the core of the Air Traffic Organization. The 

responsibilities of Air Traffic Services are now distributed among several 

offices, including System Operations Services and Terminal Services. The 

responsibilities of Research and Acquisitions are distributed among several 

offices, including Technical Operations Services and En Route and Oceanic 

Services. In addition, the Air Traffic Organization includes Safety Services, 

which is its focal point for safety, quality assurance, and quality control and 

is the primary interface with FAA’s Office of Regulation and Certification.

FAA’s Office of Regulation and Certification has responsibility for certifying 

and regulating aircraft and its equipment. The following 3 offices within the 

Office of Regulation and Certification are involved in the certification of 

aircraft equipment:

• Aircraft Certification Service (aircraft certification office) is responsible 

for administering safety standards for aircraft and aircraft equipment 

that are manufactured in the United States. 

• Flight Standards Service is responsible for granting operational 

approval to air carriers that plan to use equipment on their aircraft.

• Air Traffic Safety Oversight Service is responsible for monitoring the 

safety of air traffic operations through the establishment, approval, and 

acceptance of safety standards and the monitoring of safety 

performance and trends. It will also improve coordination between the 

Office of Regulation and Certification and the Air Traffic Organization.

In addition to the internal FAA stakeholders, the approval of air traffic 

control (ATC) systems can also involve a number of other external 

stakeholders. FAA generally makes the decision about which other 

stakeholders will be involved in approving ATC systems for safe use in the 

national airspace system. For example, stakeholders involved in approving 

ATC systems may include

• technical experts; 

• ground system developers; 

• manufacturers of aircraft equipment; 
Page 9 GAO-05-11 Air Traffic Control

• aviation industry groups; 

• general aviation; and 

• users, such as controllers and maintenance technicians.

FAA also regularly requests RTCA, a private, not-for-profit corporation, to 

develop consensus-based performance standards for the aircraft 

equipment component of ATC systems. RTCA functions as a federal 

advisory committee that provides recommendations used by FAA as the 

basis for policy, program, and regulatory decisions and by the private 

sector as the basis for development, investment, and other business 

decisions.

In this report, we focus on the approval of the 5 ATC systems described in 

table 1 and further discussed in appendixes II through VI.
Page 10 GAO-05-11 Air Traffic Control

Table 1: FAA Systems Used as Case Illustrations

Source: FAA.

System Description

Airport Surface Detection Equipment – Model X

(ASDE-X)

ASDE-X is a traffic management system that air traffic controllers use to track 

aircraft and vehicle movement at an airport. ASDE-X was developed to 

prevent runway accidents. It also provides aircraft identification from an 

airport’s surface. ASDE-X uses a combination of surface movement radar 

and sensors to display aircraft position on an ATC tower display. The 

integration of these sensors provides accurate, up-to-date, and reliable data 

to improve airport safety in all weather conditions. 

Controller-Pilot Data Link Communications (CPDLC) CPDLC allows pilots and controllers to transmit digital messages directly 

between an FAA ground automation system and suitably equipped aircraft. 

CPDLC is a new way for controllers and pilots to communicate that is 

analogous to e-mail. This system is meant to alleviate voice congestion 

problems and increase controller efficiency. 

Local Area Augmentation System (LAAS) LAAS is a precision approach and landing system that relies on the Global 

Positioning System (GPS) to broadcast highly accurate information to aircraft 

on the final phases of a flight. LAAS is being developed specifically to 

augment GPS satellites to support precision approaches and landing 

capability to aircraft operating within a 20- to 30-mile radius of the airport. 

LAAS approaches will be designed to avoid obstacles, restricted airspace, 

noise-sensitive areas, or congested airspace. 

Standard Terminal Automation Replacement System 

(STARS)

STARS replaces controller workstations with new color displays, processors, 

and computer software at the FAA and the Department of Defense terminal 

ATC facilities. FAA’s goal for STARS is to provide an open, expandable 

terminal automation platform that can accommodate future air traffic growth 

and allow for the introduction of new hardware- and software-based tools to 

promote safety, maximize operational efficiency, and improve controllers’ 

productivity. 

Wide Area Augmentation System (WAAS) WAAS is a GPS-based navigation and landing system that is meant to 

improve safety by providing precision guidance to aircraft for all phases of 

flight at thousands of airports and landing strips where there is no groundbased landing capability. WAAS consists of 25 ground reference stations, 2 

leased geostationary satellites, 2 master stations, and 4 uplink stations. The 

ground reference stations are strategically positioned across the United 

States to collect GPS satellite data. WAAS is designed to improve the 

accuracy, integrity, and availability of information coming from GPS satellites 

and to correct signal errors caused by solar storms, timing, and satellite 

errors. Unlike conventional ground-based navigation aids, WAAS provides 

curved precision approach paths in order to avoid obstacles, restricted 

airspace, noise-sensitive areas, and congested airspace.
Page 11 GAO-05-11 Air Traffic Control

FAA Has Separate 

Processes for 

Approving Ground 

Systems and Certifying 

Aircraft Equipment

FAA has separate processes for approving ground systems and certifying 

aircraft equipment for safe use in the national airspace system. FAA’s 

process for approving ground systems, such as radar systems, is done in 

accordance with policies and procedures in FAA’s Acquisition Management 

System.5

 This process involves a determination by FAA’s Air Traffic 

Organization regarding whether a vendor is in compliance with contract 

requirements and/or FAA operational requirements, followed by a rigorous 

test-and-evaluation process to ensure that the new system will operate 

safely in the national airspace system. In contrast, the process for certifying 

aircraft equipment, which is usually developed by private companies, is 

done in accordance with Federal Aviation Regulations, with FAA serving as 

the regulator. If an ATC system has both a ground system and aircraft 

equipment, as was the case for 3 of the 5 systems we reviewed, then the 

system must go through both processes before it is approved for safe use in 

the national airspace system.

Ground System Approval 

Process

The approval of a ground system focuses on safety and is done in 

accordance with FAA contract documents and policies and procedures that 

are part of the agency’s Acquisition Management System. Most ground 

systems that provide air traffic services and air navigation services are 

developed, owned, and operated by FAA. Prior to November 2003, FAA’s 

Research and Acquisitions and Air Traffic Service offices were responsible 

for the approval of ground systems. Currently, FAA’s Air Traffic 

Organization has primary responsibility for the approval of ground 

systems. FAA’s ground system approval process includes the following six 

phases—concept of operations, requirements setting, design and 

development, test and evaluation, operational readiness, commissioning—

and involves various stakeholders, which are also noted below.

• Concept of operations: The ground system approval process begins with 

the concept of operations phase. If the system being developed has both 

a ground system and aircraft equipment, FAA’s Office of Regulation and 

Certification, Air Traffic Services Office, and Acquisitions Office may

5

FAA’s Acquisition Management System was created in response to a statutory mandate in 

1995 that required FAA to implement a new acquisition management system that is intended 

to provide for more timely and cost-effective acquisitions.
Page 12 GAO-05-11 Air Traffic Control

work together to develop the concept of operations.6 During this phase, 

FAA generally identifies and defines a service or capability to meet a

particular need in the national airspace system and may involve other 

stakeholders, such as air traffic controllers.7 FAA also defines the roles 

and responsibilities of key participants, such as controllers and 

maintenance technicians, and the key elements of the required 

capability. The concept of operations phase is not a static process. As 

FAA obtains more information about the system it develops, the 

concept is revised to reflect the new information even though the next 

phase of the process may have already begun. Potential stakeholders in 

this phase include FAA’s Office of Regulation and Certification, FAA’s 

Air Traffic Organization, aircraft manufacturers, aviation industry 

associations, airlines, air traffic controllers, maintenance technicians, 

manufacturers of aircraft equipment, ground system developers, and 

representatives of general aviation.

• Requirements setting: During the requirements-setting phase, FAA 

establishes a minimum set of requirements, including safety objectives, 

and specifies how well the new system must perform its intended 

functions. For example, it was during this phase that FAA established 

WAAS’ and LAAS’ integrity requirement—which is that the system 

cannot fail to warn pilots of misleading information that could 

potentially create hazardous situations more than once in 10 million 

approaches. After analyzing the initial requirements and comparing the 

cost, benefits, schedule, and risk of various solutions, FAA sets final 

requirements and presents them to the Joint Resources Council as part 

of the investment plan.8

 After the council has approved the requirements 

for the new system, FAA will issue a request for proposals, evaluate the 

offers received, and select a contractor to design a system based on the 

requirements set by FAA. Potential stakeholders in this phase include 

FAA’s Office of Regulation and Certification, FAA’s Air Traffic 

Organization, aircraft manufacturers, aviation industry associations, 

airlines, air traffic controllers, maintenance technicians, manufacturers 

6

FAA’s Air Traffic Services and Acquisitions Offices have recently become part of FAA’s 

newly created Air Traffic Organization.

7

However, sometimes the need for a service or capability originates in the private sector.

8

The Joint Resources Council consists of senior FAA executives who discuss and approve 

agency mission needs and investments in acquisition programs.
Page 13 GAO-05-11 Air Traffic Control

of aircraft equipment, ground system developers, and representatives of 

general aviation.

• Design and development: The design and development of ground 

systems is generally completed by a contractor and monitored by FAA. 

During this phase, the contractor conducts preliminary and critical 

design reviews, which include plans for how it will conduct the testing 

phase. FAA must approve these plans before the contractor can proceed 

to the next phase. Potential stakeholders in this phase include FAA, 

ground system developers, air traffic controllers, and maintenance 

technicians.

• Test and evaluation: After FAA has approved the design and 

development of the system, it is ready to be tested and evaluated. The 

testing and evaluation of ground systems typically includes three major 

tests: development tests, operational tests, and an independent 

operational test and evaluation. Development testing is performed by 

the contractor to verify compliance with contractual requirements and 

is overseen by FAA. Operational testing is performed by FAA and is 

designed to demonstrate that a new system is operationally effective 

and suitable for use in the national airspace system. An independent 

operational test and evaluation is a full system-level evaluation 

conducted by FAA in an operational environment to confirm the 

operational readiness of a system to be part of the national airspace 

system. Potential stakeholders in this phase include FAA, ground system 

developers, air traffic controllers, and maintenance technicians.

• Operational readiness: During the operational readiness phase, FAA 

personnel are trained to operate and maintain the new system, usually in 

conjunction with its predecessor system. Following operational 

readiness approval, the system is ready to be commissioned. Potential 

stakeholders in this phase include FAA, ground system developers, air 

traffic controllers, and maintenance technicians.

• Commissioning: The commissioning phase ensures that the new 

ground system as installed meets the intended mission and operational 

requirements and is fully supported by the national airspace system 

infrastructure. Potential stakeholders in this phase include FAA, ground 

system developers, air traffic controllers, and maintenance technicians.
Page 14 GAO-05-11 Air Traffic Control

Aircraft Equipment 

Certification Process

In contrast to the ground system approval process, certification of aircraft 

equipment is done in accordance with procedures outlined in the Federal 

Aviation Regulations, Title 14, Code of Federal Regulations, Part 21. Under 

Title 49, Section 44704, of the U.S. Code, FAA has the authority to issue type 

certificates, supplemental type certificates, and production certificates, 

among others, for aircraft and equipment that will be used in the national 

airspace system.9

 Unlike the approval of ground systems, which FAA 

accomplishes with the help of a contractor, FAA is the regulator of aircraft 

equipment and is not typically involved in the development of the 

equipment. An applicant, such as a manufacturer of aircraft equipment, 

generally brings fully developed aircraft equipment to FAA for certification. 

The aircraft equipment certification process includes the following five 

phases—concept of operations, requirements setting, design and 

production approval, installation approval, and operational approval—and 

involves several stakeholders, which are also noted below: 

• Concept of operations: Like the ground system approval process, the 

aircraft equipment certification process generally begins with the 

concept of operations phase, when the aircraft equipment is part of an 

ATC system. If the aircraft equipment certification process is not 

associated with the approval of a new ground system, then the 

certification process may begin with an idea for better equipment. 

During this phase, FAA, sometimes with the help of industry, identifies 

and defines a service or capability to meet a particular need in the 

national airspace system.10 Potential stakeholders in this phase include 

FAA’s Office of Regulation and Certification, FAA’s Air Traffic 

Organization, aircraft manufacturers, aviation industry associations, 

airlines, air traffic controllers, maintenance technicians, manufacturers 

of aircraft equipment, ground system developers, and representatives of 

general aviation.

• Requirements setting: Once FAA has identified the need for a new 

system with aircraft equipment, FAA determines the requirements for

9

A type certificate is issued when an aircraft design is certified to meet applicable 

airworthiness standards. A supplemental type certificate is issued when an applicant has 

received FAA’s approval to modify an aircraft from its original design. A production 

certificate applies to a company’s manufacturing process and states that company can 

produce products consistent with the approved design. 

10However, sometimes the need for a service or capability originates in the private sector.
Page 15 GAO-05-11 Air Traffic Control

the aircraft equipment.11 In some cases, the requirements for aircraft 

equipment may already exist in the Federal Aviation Regulations. In 

other cases, FAA may ask RTCA to develop the requirements, including 

safety requirements, which are referred to as minimum operating 

performance standards. RTCA typically takes 1 to 5 years to develop 

the standards because of the need to reach consensus between FAA 

and the industry and the increasing complexity of systems being 

developed today. According to a RTCA official, the time required to 

develop recommended standards is a function of many variables, 

including urgency of the situation and the commitment and availability 

of government and industry volunteers to collaboratively develop the 

standards. For example, in the case of WAAS, RTCA began setting 

performance standards in 1994, completed the original version of the 

standards in January 1996, and completed the most recent version of 

WAAS performance standards in November 2001. Potential 

stakeholders in this phase include FAA’s Office of Regulation and 

Certification, FAA’s Air Traffic Organization, aircraft manufacturers, 

aviation industry associations, airlines, air traffic controllers, 

maintenance technicians, manufacturers of aircraft equipment, ground 

system developers, and representatives of general aviation.

• Design and production approval: The requirements/performance 

standards, most often developed by RTCA, typically form the basis for a 

technical standard order, which FAA uses to grant design and 

production approval for most new aircraft equipment developed in 

support of national airspace system modernization efforts. Technical 

standard orders are FAA’s requirements for materials, parts, processes, 

and appliances used on civil aircraft.12 Most aircraft manufacturers want 

technical standard orders because they make installation approval 

simpler and less costly and allow for operation in any type of aircraft. 

Technical standard orders are issued for items ranging from safety belts 

to navigation equipment. If the applicant successfully completes the 

design and production approval phase, FAA provides the applicant with 

11Requirements may include regulation-based requirements, performance standards in 

technical standard orders, and/or international requirements. 

12If a technical standard order does not exist for aircraft equipment, the applicant will be 

required to obtain design and installation approval under the type certificate or 

supplemental type certificate design approval process, which involves many of the same 

activities involved in the technical standard order authorization process. Upon completion 

of this phase, FAA issues a type certificate or supplemental type certificate for one type of 

aircraft. 
Page 16 GAO-05-11 Air Traffic Control

a technical standard order authorization letter, which states that the 

applicant has met a specific technical standard order and the product is 

now ready for the installation approval phase. Potential stakeholders in 

this phase include FAA’s Aircraft Certification Service, manufacturers of 

aircraft equipment, and aircraft manufacturers.

• Installation approval: After receiving a technical standard order 

authorization for new aircraft equipment, the initial applicant must 

receive installation approval from FAA before the aircraft equipment 

may be used in the national airspace system. To receive installation 

approval, the applicant submits a certification plan and test plan to one 

of FAA’s aircraft certification offices for review and approval. In 

addition, the applicant conducts ground and flight tests under FAA’s 

supervision to ensure that the new equipment operates properly upon 

installation. Once the tests are completed to FAA’s satisfaction, FAA 

issues a supplemental type certificate, which is evidence of FAA’s 

approval to modify an aircraft from its original design. Potential 

stakeholders in this phase include FAA’s Aircraft Certification Service, 

manufacturers of aircraft equipment, and aircraft manufacturers.

• Operational approval: Finally, for the aircraft equipment to become 

certified for use in the national airspace system by air carrier operators, 

operational approval is also needed from FAA. To obtain operational 

approval, the applicant must successfully demonstrate, among other 

things, that the pilots are properly trained to use the aircraft equipment 

and that maintenance personnel are properly trained to maintain the 

equipment. Potential stakeholders in this phase include FAA’s Flight 

Standards Service, airlines, and representatives of general aviation.

FAA Faced Challenges 

in Approving Several 

ATC Systems

FAA faced challenges in approving systems for safe use in the national 

airspace system that contributed to cost growth, delays, and performance 

shortfalls in deploying these systems. We identified three specific
Page 17 GAO-05-11 Air Traffic Control

challenges through the review of 5 ATC systems and our past work.13 These 

challenges are the need to

• involve appropriate stakeholders, such as users and technical experts, 

throughout the approval process; 

• ensure that the FAA offices that have responsibility for approving 

ground systems and certifying aircraft equipment effectively coordinate 

their efforts for integrated systems; and

• accurately estimate the amount of time needed to meet complex 

technical requirements at the beginning of the design and development 

phase. 

Although most of the challenges we found relate to the ground system 

approval process, RTCA and the Aerospace Commission have identified 

challenges with FAA’s aircraft equipment certification process. For 

example, RTCA found that there was a need for better internal FAA 

communication and coordination, including the establishment of an 

organizational focal point to provide coordinated responses to all matters 

related to ground systems and aircraft equipment. In addition, the 

Aerospace Commission found that FAA’s regulatory process needs to be 

streamlined to enable the timely development of regulations needed to 

address new technologies.

FAA Did Not Always 

Adequately Involve 

Appropriate Stakeholders, 

Such as Users and Technical 

Experts, Throughout Its 

Approval Process 

FAA failed to adequately involve appropriate stakeholders, such as air 

traffic controllers and maintenance technicians, for 3 of the 5 systems we 

reviewed. For example, FAA did not adequately involve controllers and 

maintenance technicians throughout the approval process of STARS, which 

will replace controller workstations with new color displays, processors, 

and computer software. Although controllers and technicians were 

involved in developing requirements for STARS in 1994 prior to the 1996 

contract award to Raytheon, the original approved acquisition plan 

provided for only limited human factors evaluation by controllers and 

13GAO, Air Traffic Control: FAA’s Modernization Efforts – Past, Present, and Future, 

GAO-04-227T (Washington, D.C.: Oct. 30, 2003); National Airspace System: Persistent 

Problems in FAA’s New Navigation System Highlight Need for Periodic Reevaluation, 

GAO/RCED/AIMD-00-130 (Washington, D.C.: June 12, 2000); and National Airspace System:

Status of FAA’s Standard Terminal Automation Replacement System, GAO-02-1071

(Washington, D.C.: Sept. 17, 2002).
Page 18 GAO-05-11 Air Traffic Control

technicians during STARS’ design and development because the aggressive 

development schedule limited the amount of time available to involve 

them.14 Consequently, FAA and Raytheon had to restructure the contract to 

address controllers’ concerns that were identified later, such as the 

inconsistency of visual warning alarms and color codes with the new 

system. According to FAA officials, not involving controllers and 

maintenance technicians in the design phase caused the agency to revise its 

strategy for acquiring and approving STARS, which contributed to STARS’ 

overall cost growth of $500 million and added 3 years to the schedule.

FAA also did not always sufficiently involve technical experts early in its 

approval process for 2 additional systems that we reviewed. For example, 

FAA did not obtain technical expertise on how to resolve the integrity 

requirement of WAAS, a navigation system for aviation that augments the 

Global Positioning System (GPS), until late in the design and development 

phase.15 FAA acknowledges that the agency’s in-house technical expertise 

was not sufficient to address the technical challenges of WAAS. Initially, 

FAA and the contractor believed they could meet the WAAS integrity 

requirement to alert the pilot in a timely manner when the system should 

not be used. However, although WAAS was being developed by an 

integrated product team that included representatives from several FAA 

offices, the team did not function effectively in resolving issues related to 

meeting an important functional requirement to alert the pilot in a timely 

manner when the system should not be used because of a possible error. 

According to FAA officials, the reason coordination did not occur was that 

the two offices had competing priorities that were not associated with 

WAAS’ development. Consequently, in 2000, FAA convened the WAAS 

Integrity Performance Panel to help it meet the integrity requirement. The 

WAAS Integrity Panel worked for about 2-1/2 years before it came up with a 

solution to the integrity requirement. In addition, in August 2000, the 

agency established an Independent Review Board, which is independent of 

the panel and included experts in satellite navigation and safety 

certification, to oversee the panel and evaluate the soundness of its efforts. 

14Human factors evaluation examines how humans interact with machines and identifies 

ways to enhance operators’ performance and minimize errors.

15GPS is a space-based, radio-navigation system consisting of a constellation of satellites and 

a network of ground stations used for monitoring and control. A minimum of 24 GPS 

satellites orbit the Earth at an altitude of approximately 11,000 miles, providing users with 

accurate information on position, velocity, and time of a GPS-equipped object, such as an 

aircraft, anywhere in the world and in all weather conditions.
Page 19 GAO-05-11 Air Traffic Control

According to a member of the WAAS Integrity Panel, if FAA had involved 

these technical groups immediately after the contract was awarded to 

Raytheon in 1996, these groups could have started devising a solution in 

1996, rather than in 2000. This lack of technical expertise contributed to a 

6-year delay in WAAS’ commissioning and a $1.5 billion increase in its 

development costs from the 1994 baseline.16

FAA also did not fully engage technical experts early in the approval 

process of LAAS, a precision approach and landing system that will 

augment GPS. According to FAA officials, meeting the LAAS integrity 

requirement to alert the pilot in a timely manner when the system should 

not be used is perhaps the most difficult part of approving this system for 

safe use in the national airspace system. According to the Department of 

Transportation’s Inspector General, although FAA had a LAAS Integrity 

Panel in place since 1996 to assist with its research and development 

activities, the panel was not formally tasked with resolving LAAS’ integrity 

issues. According to one satellite navigation expert and the Department of 

Transportation’s Inspector General, focusing the LAAS Integrity Panel on 

resolving the integrity requirement early in the approval process may have 

enabled FAA to develop a quicker solution.17 In 2003, FAA focused the 

LAAS Integrity Panel on developing a solution to meet the integrity 

requirement. However, FAA and another satellite expert maintain that the 

technical complexity of this problem is the main reason that LAAS is not 

commissioned. According to FAA officials, the need to validate integrity 

requirements and further software development has resulted in FAA 

placing LAAS in its research and development program and suspending 

funding for fiscal year 2005.

In contrast, FAA faced fewer schedule and cost problems in approving 

ASDE-X for use in the national airspace system. This was, in part, because 

FAA included stakeholders early and throughout the approval process and 

because program managers had strong technical expertise. The ASDE-X 

16In addition, some development costs, such as required design changes discovered during 

early development, were not included in the 1994 baseline. When these development costs 

were captured in the 1999 baseline and then again in the 2004 baseline, there was a net 

increase in development costs of $1.5 billion through 2028. However, these costs do not 

include operating and maintaining geo satellites, which were not part of WAAS’ original 1994 

baseline and added an additional $1.3 billion in development costs.

17Department of Transportation’s Inspector General, FAA Needs to Reset Expectations for 

LAAS Because Considerable Work Is Required before It Can Be Deployed for Operational 

Use, AV-2003-006 (Dec. 16, 2002).
Page 20 GAO-05-11 Air Traffic Control

program office brought in stakeholders, including maintenance technicians 

and air traffic controllers, during the concept of operations phase and 

continued to involve them during requirements setting, design and 

development, and test and evaluation. FAA also brought ASDE-X 

stakeholders together at technical meetings to provide input on ASDE-X 

design and development, which allowed the ASDE-X program office to 

design a system that met requirements and incorporated stakeholders’ 

needs. By obtaining the input of controllers and technicians at the 

beginning of the approval process, FAA was able to ensure that ASDE-X 

requirements were set at appropriate levels and not overspecified or 

underspecified. Some stakeholders commented that the program 

managers’ strong technical expertise was one reason that ASDE-X’s 

requirements were set appropriately. As a result, this system was initially 

commissioned only 5 months behind schedule and its cost increased 

moderately from $424 million to $510 million.

FAA Did Not Always 

Effectively Coordinate Its 

Certification and Approval 

Processes 

FAA did not always effectively coordinate its certification and approval 

processes for CPDLC, WAAS, and LAAS. Coordination between FAA’s 

offices responsible for approval of ground systems and certification of 

aircraft equipment is becoming increasingly important given that more and 

more ATC systems have both ground systems and aircraft equipment. 

However, we found that coordination was not effective on CPDLC Build 

1A, which allows pilots and controllers to transmit digital data messages 

directly between FAA ground automation systems and suitably equipped 

aircraft.18 In the interest of meeting the original cost and schedule 

estimates, FAA awarded the contract before it had a full understanding of 

system requirements. Requirements that specify how the ground system 

and aircraft equipment would operate together were not yet completed 

prior to award of the Build 1A contract. Consequently, changes needed to 

be made after the contract was awarded. New hardware requirements, 

software requirements, and other system requirement changes were added, 

which increased CPDLC’s costs by $41 million, almost 61 percent of the 

total cost increases associated with CPDLC. 

The lack of effective coordination among FAA offices responsible for 

approving WAAS also contributed to delays and increased costs in 

18Build 1A was the second CPDLC development stage, yet to be completed, that was 

designed to increase the CPDLC message set and include assignment of speeds, headings, 

and altitudes as well as a route clearance function. 
Page 21 GAO-05-11 Air Traffic Control

commissioning WAAS. Although WAAS was being developed by an 

integrated product team that included representatives from various FAA 

offices, the team did not function effectively in resolving issues related to 

meeting an important functional requirement to alert the pilot in a timely 

manner when the system should not be used because of a possible error. 

According to FAA officials, the reason coordination was not effective was 

because the two offices had competing priorities that were not associated 

with development of WAAS. Consequently, it was not until September 1999, 

when the aircraft certification office became fully involved, that FAA 

recognized that its solution to meet WAAS’ integrity requirement was not 

sufficient and that it did not have the technical expertise needed to develop 

a solution. This lack of coordination contributed to a 6-year delay in WAAS’ 

commissioning and a $1.5 billion increase in its development costs.

LAAS is another example of how FAA did not effectively coordinate its 

efforts. For example, FAA’s Office of Regulation and Certification 

completed the design and production approval of LAAS aircraft equipment 

without effectively coordinating with the offices responsible for acquisition 

to determine the consequences of certifying aircraft equipment before 

approval of the associated ground system. According to an FAA official, 

once the Office of Regulation and Certification has given design and 

production approval to the LAAS aircraft equipment, it is not possible to 

make a change to the requirements for the aircraft equipment so that they 

are better integrated with the associated LAAS ground system. 

Consequently, LAAS ground system developers may have to make more 

costly and time-consuming changes to the ground system than would have 

been necessary if the Office of Regulation and Certification and 

acquisitions offices had coordinated their efforts.

FAA Did Not Always 

Prepare Accurate Estimates 

of the Amount of Time 

Needed to Meet Complex 

Technical Requirements 

We have reported in the past that when FAA attempts to combine different 

phases of system development in an effort to more quickly implement the 

systems to meet milestones, it repeatedly experiences major performance 

shortfalls and rework, which leads to schedule delays and cost increases.19

We found that WAAS, STARS, and LAAS all experienced delays and cost 

increases in part because FAA did not prepare accurate estimates of the 

amount of time needed to meet complex technical requirements, leading to 

19GAO, National Airspace System: Problems Plaguing the Wide Area Augmentation 

System and FAA’s Actions to Address Them, GAO/T-RCED-00-229 (Washington, D.C.: June 

29, 2000).
Page 22 GAO-05-11 Air Traffic Control

an accelerated schedule that sometimes failed to include activities such as 

human factors evaluations and technical expert consultations. For 

example, in 1994, in response to the concerns of government and aviation 

groups, FAA accelerated implementation of WAAS milestones from 2000 to 

1997. FAA planned to develop, test, and deploy WAAS within 28 months, an 

unrealistic goal given that software development alone was expected to 

take 24 to 28 months. It was not until July 2003, over 6 years later, that FAA 

was able to commission WAAS for initial operating capability. The 

accelerated schedule contributed to the 6-year delay in the commissioning 

of the system because the schedule itself was unrealistic and additional 

design work needed to be completed. During that time, the cost to develop 

the system increased about $1.5 billion, and the system has yet to meet its 

original performance goal of providing pilots with the ability to navigate 

down to 200 feet during their approach to the runway. 

FAA also accelerated the schedule for STARS in 1995. FAA’s approach to 

commissioning STARS was oriented to rapid deployment to meet critical 

needs for new equipment. To meet these needs, FAA compressed its 

original development and testing schedule from 32 to 25 months. 

Consequently, this acceleration in schedule left only limited time for human 

factors evaluations and, according to FAA officials, contributed to STARS’ 

overall cost growth of $500 million and added 3 years to the first 

deployment because the agency had to revise its strategy for acquiring and 

approving STARS.

Although FAA had not developed a solution for meeting the integrity 

requirement, FAA also accelerated the LAAS schedule in 1999 by setting 

system milestones before completely designing the system. FAA originally 

planned to deploy LAAS in 2002 but has since moved it to fiscal year 2009 

because the system’s software development is not complete and a solution 

for meeting LAAS’ integrity requirements has yet to be developed. 

RTCA and the Aerospace 

Commission Found 

Challenges with FAA’s 

Process for Approving 

Ground Systems and 

Certifying Aircraft 

Equipment

RTCA and the Aerospace Commission also identified challenges with FAA’s 

process for approving ground systems and certifying aircraft equipment. In 

1998, at the request of the FAA Administrator, RTCA reviewed FAA’s 

certification/approval process to determine if it could be made more 

responsive to the changing state of aviation, including its more integrated 

technologies. RTCA found that FAA’s ground system approval process and 

aircraft equipment certification process took too long and cost too much, 

and RTCA made several recommendations to improve the processes. For 

example, in 2001, RTCA recommended that FAA implement a coordinated 
Page 23 GAO-05-11 Air Traffic Control

approval process that, among other things, would ensure that all 

stakeholders, including those outside FAA’s program offices, participate in 

all phases of the approval process. Specifically, similar to our finding that 

the FAA offices that had responsibility for approving ground systems and 

certifying aircraft equipment did not always effectively coordinate their 

efforts, RTCA found that there was a need for better internal FAA 

communication and coordination, including the establishment of an 

organizational focal point to provide coordinated responses to all matters 

related to ground systems and aircraft equipment. RTCA also found that 

there was a need for an earlier and better exchange of information between 

FAA and those involved in the approval and certification processes from 

outside FAA, such as manufacturers of aircraft equipment.20

In 2000, Congress asked the Commission on the Future of the U.S. 

Aerospace Industry to study the health of the aerospace industry and 

identify actions that the United States needs to take to ensure the industry’s 

health. As part of this study, the Aerospace Commission reviewed FAA’s 

certification process for aircraft equipment and made recommendations. 

The Aerospace Commission found that FAA’s certification of new aircraft 

technologies has become uncertain in terms of time and cost and 

recommended that FAA’s regulatory process be streamlined to enable the 

timely development of regulations needed to address new technologies. 

According to the Aerospace Commission, instead of focusing on rules and 

regulations that dictate the design and approval of equipment, FAA should 

focus on certifying that manufacturing organizations have safety built into 

their processes for designing, testing, and ensuring the performance of an 

overall system. The commission believed that such an approach would 

allow FAA personnel to better keep up with technological progress by 

becoming less design-specific and more safety-focused.

FAA Has Taken Action 

to Improve Its Process 

for Approving ATC 

Systems 

FAA has taken action to address two of the three management challenges 

that we identified. However, FAA has not taken action to ensure that all 

stakeholders, such as air traffic controllers, maintenance technicians, 

technical experts, and industry representatives, are involved throughout 

the ground system approval process. FAA has also taken some action to 

address recommendations made by RTCA and the Aerospace Commission. 

Examples of some of the actions FAA has taken that address the 

20RTCA, Final Report of the Task Force 4: Certification (1999) and RTCA Task Force 4 – 

Certification Implementation Plans and Responsibilities (2001).
Page 24 GAO-05-11 Air Traffic Control

management challenges that we found as well as RTCA and Aerospace 

Commission recommendations are discussed below:

• Coordinating FAA’s acquisitions offices and Office of Regulation and 

Certification efforts for approving systems with ground and aircraft 

components: FAA officials believe that the agency’s new Safety 

Management System, which is designed to formalize the agency’s safety 

process, will also improve coordination among FAA internal 

stakeholders once it is implemented. FAA stated that coordination 

would improve because as part of the new Safety Management System 

the agency plans to realign its organizational structure to create a formal 

link between the Air Traffic Organization and the Office of Regulation 

and Certification. Within the Office of Regulation and Certification,

there is the newly created Air Traffic Safety Oversight Service, which 

oversees the safety operations of the Air Traffic Organization and 

collaborates with the Air Traffic Organization’s Safety Services. In 

addition, according to FAA officials, both ground systems and aircraft 

equipment will be more consistently assessed for their effect on safety 

as safety terminology is standardized. FAA expects full implementation 

to take 3 to 5 years. We are reserving judgment on whether this change 

will fully address the challenge because of the early state of this effort 

and because FAA’s problems with internal coordination when approving 

ATC systems are long-standing. In addition, because FAA has 

historically faced internal and external coordination challenges in 

approving ATC systems for safe use in the national airspace, we believe 

that as FAA moves forward with the agency’s new Safety Management 

System, it should, in the interim, develop plans that describe how both 

internal and external coordination will occur on a system-specific basis. 

In addition, plans to include external stakeholders are particularly 

important since the Safety Management System is not intended to 

address this challenge.

• Estimating the amount of time needed to meet complex technical 

requirements: During the development of WAAS and STARS, FAA 

adopted an incremental approach to developing and testing these 

systems to get them back on track, which is referred to as the “build a 

little, test a little” or spiral development approach. For example, to get 

WAAS back on track, FAA decided to take a more incremental approach 

to implementing the new navigation system—focusing more on the 

successful completion of research and development before starting 

system approval. In particular, FAA allowed time for collecting and 

evaluating data on key system performance requirements like the WAAS 
Page 25 GAO-05-11 Air Traffic Control

integrity requirement before moving forward. FAA officials 

acknowledged that the manner in which FAA decided to implement 

WAAS development before implementing this incremental approach 

was a high-risk approach and was a primary issue underlying the 

system’s problems. Some aviation stakeholders believe this approach is 

advantageous because, although it can increase costs initially, money 

can be saved in the long run because the approach may help to avoid 

mistakes that are very costly to fix once a system has been developed. 

This approach also helps to ensure that the necessary building blocks of 

a system are tested along the way through the early and ongoing 

involvement of key stakeholders, those who will use and maintain the 

system. These stakeholders are key to identifying critical omissions and 

issues that could prevent a system from operating as intended.21

As previously discussed, RTCA and the Aerospace Commission reviewed 

FAA’s approval process and made a number of recommendations to 

improve it. FAA has taken some action to address these recommendations. 

For example:

• In response to RTCA’s recommendation to implement a process in 

which the regulators and applicants come to an early and clear 

agreement on their respective roles, responsibilities, expectations, 

schedules, and standards to be used in certification projects, FAA issued 

The FAA and Industry Guide to Avionics Approval in 2001, which is 

intended to help FAA reduce the time and cost for the certification of 

aircraft equipment. This guide describes how to plan, manage, and 

document an effective, efficient aircraft equipment certification process 

and how to develop a working relationship between FAA and the 

applicant. In addition, as part of the 1999 FAA and Industry Guide to 

Product Certification, FAA encourages the manufacturers of aircraft 

equipment to develop a Partnership for Safety Plan that defines roles 

and responsibilities, describes how the certification process will be 

conducted, and identifies the milestones for completing the 

certification. A WAAS aircraft equipment manufacturer said that the 

certification of the WAAS aircraft equipment it developed went 

smoothly, primarily because of this up-front agreement with FAA. 

Although FAA’s actions address the aircraft equipment certification 

21GAO-04-227T and National Airspace System: FAA Has Implemented Some Free Flight 

Initiatives, but Challenges Remain, GAO/RCED-98-246 (Washington, D.C.: Sept. 28, 1998).
Page 26 GAO-05-11 Air Traffic Control

process, it does not have a similar process for its ground system 

approval process.

• In response to RTCA’s recommendation to establish an organizational 

focal point to provide one-stop service to users, industry, and other 

governments in all matters related to advanced ground electronics and 

aircraft equipment, FAA has completed a Web site that provides a broad 

range of information on the certification process for aircraft equipment. 

However, there is still no focal point to which industry can address 

questions about the approval process and be assured of getting a fully 

coordinated FAA answer.

• In response to the Aerospace Commission’s recommendation to 

streamline its aircraft equipment certification process to ensure timely 

development of regulations needed to address new technologies and to 

focus on certifying that manufacturing organizations have built safety 

into their processes for designing, testing, and ensuring the performance 

of an overall system, FAA proposed creating an Organizational 

Designation Authorization program in January 2004. The program would 

expand the approval functions of FAA organizational designees,22

standardize these functions to increase efficiency, and expand eligibility 

for organizational designees. 

Conclusions FAA did not always include stakeholders throughout the process for 

approving ATC systems for safe use in the national airspace system. 

Including stakeholders is particularly important because the new ATC 

systems are more integrated today than in the past and thus require more 

coordination among all the stakeholders, particularly FAA’s Office of 

Regulation and Certification and the recently created Air Traffic 

Organization, but also between FAA and other stakeholders, such as 

technical experts, controllers, and maintenance technicians. When 

decisions regarding integrated ATC systems are made in isolation, they may 

contribute to the ineffective use of resources and time. We found that 3 of 

the 5 ATC systems we reviewed experienced cost growth and schedule 

delays, in part, because FAA did not always involve all necessary 

stakeholders, such as controllers and technical experts, throughout the 

approval process. In 2001, RTCA recommended that FAA implement a 

22Organizational designees perform functions for FAA to minimize FAA’s administrative 

burden. 
Page 27 GAO-05-11 Air Traffic Control

coordinated approval process that, among other things, would ensure that 

all stakeholders, including those outside FAA’s program offices, participate 

in all phases of the approval process. We agree with RTCA’s 

recommendation, which FAA has not fully implemented, and believe that 

fully implementing it would help address some of the challenges we found 

with FAA’s approval and certification processes. 

In addition, although FAA’s new Safety Management System and the 

planned alignment between FAA’s Air Traffic Organization and Office of 

Regulation and Certification have the potential to improve FAA’s internal 

coordination, FAA has just begun implementing these initiatives with full 

implementation 3 to 5 years away. FAA also has historically faced internal 

coordination challenges in approving ATC systems for safe use in the 

national airspace system as we found for each of the 3 integrated systems 

that we reviewed. We believe that the implementation of the Safety 

Management System, coupled with the new formal link between FAA’s Air 

Traffic Organization and Office of Regulation and Certification, will give 

FAA the opportunity to improve its internal coordination among its offices 

that are responsible for ground system approval and aircraft equipment 

certification. However, the system will not be implemented until 3 to 5 

years. Therefore, because of FAA’s history of internal and external 

coordination challenges, such as the lack of effective coordination between 

FAA offices responsible for approving WAAS, which contributed to WAAS’ 

cost increase of about $1.5 billion and schedule delays of 6 years, we 

believe that specific plans for improving coordination both internally and 

externally on a system-specific basis are needed now. 

Recommendation for 

Executive Action

To ensure that key stakeholders, such as air traffic controllers, 

maintenance technicians, and technical experts, outside FAA’s acquisitions 

offices and Office of Regulation and Certification, are involved early and 

throughout FAA’s ground system approval process and to ensure better 

internal coordination between FAA’s offices responsible for approving 

ground systems and certifying aircraft equipment, we recommend that the 

Secretary of Transportation direct the Administrator of FAA to develop 

ATC system-specific plans early in the approval process that specify how 

and when the approving and certifying offices within FAA and other 

stakeholders, including controllers, maintenance technicians, technical 

experts, and industry representatives, will meet to ensure coordination.
Page 28 GAO-05-11 Air Traffic Control

Agency Comments We provided a draft of this report to the Secretary of Transportation for 

review and comment. FAA generally agreed with our findings and 

recommendation and provided technical corrections, which we 

incorporated as appropriate. FAA also commented that it has started to 

take actions to improve its coordination efforts for integrated ATC systems.

We are sending copies of this report to interested congressional 

committees, the Secretary of Transportation, and the FAA Administrator. 

We will also make copies available to others on request. In addition, the 

report will be available at no charge on the GAO Web site at 

http://www.gao.gov. Should you or your staff have questions on matters 

discussed in this report, please contact me on (202) 512-2834 or at 

siggerudk@gao.gov. GAO contacts and key contributors to this report are 

listed in appendix VII.

Sincerely yours,

Katherine Siggerud

Director, Physical Infrastructure Issues
Page 29 GAO-05-11 Air Traffic Control

Appendix I

Objectives, Scope, and Methodology ApApenednxidexiIs

To complete our first objective, to describe FAA’s process for approving air 

traffic control (ATC) systems for safe use in the national airspace system, 

we obtained and analyzed documents from the Federal Aviation 

Administration (FAA) and RTCA’s1

 1999 report that discussed FAA’s 

process for certifying aircraft equipment and approving ground systems. 

We also interviewed FAA officials, contractors, industry experts, and 

unions representing air traffic controllers and maintenance technicians 

that are involved in approving ATC systems. 

To complete our second objective, to describe the challenges FAA has 

faced approving ATC systems and how those challenges affected the cost, 

schedule, and performance estimates of the systems, we conducted case 

illustrations on 5 of FAA’s 25 air traffic control systems that are currently 

receiving funding: 

• Airport Surface Detection Equipment - Model X (ASDE-X), 

• Controller-Pilot Data Link Communications (CPDLC),

• Local Area Augmentation System (LAAS),

• Standard Terminal Automation Replacement System (STARS), and 

• Wide Area Augmentation System (WAAS).

We selected these 5 systems because collectively they accounted for about 

46 percent of FAA’s ATC modernization costs in fiscal year 2002 and 3 of the 

5 systems are integrated—that is, they require the approval of the ground 

systems as well as aircraft equipment. To select the 5 case illustration 

systems, we used FAA’s capital investment project data file. We met with 

knowledgeable FAA officials to discuss issues related to the accuracy and 

completeness of the data file, which was deemed adequate for the purpose 

of our work. We also met with knowledgeable FAA officials to determine 

the number of ATC systems from the data file that needed to be approved 

1

Organized in 1935 and once called the Radio Technical Commission for Aeronautics, RTCA 

is today known just by its acronym. RTCA is a private, not-for-profit corporation that 

develops consensus-based performance standards for ATC systems. RTCA serves as a 

federal advisory committee and its recommendations are the basis for a number of FAA’s 

policy, program, and regulatory decisions. In 1999, RTCA published its Final Report of the 

Task Force 4: Certification. In 2001, RTCA published RTCA Task Force 4 – Certification 

Implementation Plans and Responsibilities.
Appendix I

Objectives, Scope, and Methodology

Page 30 GAO-05-11 Air Traffic Control

before entry into the national airspace system. For each of the case 

illustrations, we reviewed FAA documents, including acquisition program 

baseline reports, Joint Resource Council decisions, and briefing 

documents. We also reviewed GAO and Department of Transportation’s 

Inspector General reports and testimonies. In addition, we interviewed 

officials from FAA program offices; RTCA; the General Aviation 

Manufacturers Association; the Air Transport Association; the Aircraft 

Owners and Pilots Association; NavCanada; Transport Canada; the MITRE 

Corporation; Boeing; Garmin; Rockwell Collins; contractors, including 

Honeywell, Raytheon, and the Sensis Corporation; industry experts; the 

WAAS Integrity Performance Panel; the LAAS Integrity Panel members; and 

unions representing air traffic controllers and maintenance technicians.

To compete our third objective, to describe actions FAA has taken to 

improve its processes for approving ATC systems, we interviewed 

representatives from FAA; RTCA; the Commission on the Future of the U.S. 

Aerospace Industry; aviation industry groups, including the General 

Aviation Manufacturers Association, the Air Transport Association, and the 

Aircraft Owners and Pilots Association; manufacturers of aircraft 

equipment, including Garmin and Rockwell Collins; Boeing; and 

contractors, including Honeywell, Raytheon, and the Sensis Corporation; 

industry experts; and unions representing air traffic controllers and 

maintenance technicians.

We conducted our review in Washington, D.C., from October 2003 through 

September 2004 in accordance with generally accepted government 

auditing standards. 
Page 31 GAO-05-11 Air Traffic Control

Appendix II

Airport Surface Detection Equipment - Model 

X Case Illustration ApendxiI

Background ASDE-X is an airport surface surveillance system that air traffic controllers 

use to track aircraft and vehicle surface movements. (See fig. 2.) ASDE-X 

uses a combination of surface movement primary radar and 

multilateration1

 sensors to display aircraft position and vehicle position on 

an ATC tower display. According to FAA, the integration of these sensors 

provides accurate, up-to-date, and reliable data for improving airport safety 

in all weather conditions. ASDE-X was developed to prevent accidents 

resulting from runway incursions,2

 which have increased since 1993. The 

number of reported runway incursions rose from 186 in 1993 to 383 in 2001. 

According to FAA, because air traffic in the United States is expected to 

double by 2010, runway incursions may pose a significant safety threat to 

U.S. aviation.

FAA expects that ASDE-X will increase the level of safety at airports and 

provide air traffic controllers with detailed information about aircraft 

locations and movement at night and in bad weather due to the (1) 

association of flight plan information with aircraft position on controller 

displays; (2) continuous surveillance coverage of the airport from arrival 

through departure; (3) elimination of blind spots and coverage gaps; and 

(4) availability of surveillance data with an accuracy and update rate 

suitable for, among other things, awareness in all weather conditions. 

1

Multilateration is achieved through the strategic placement of sensors around the airport 

grounds to report the location of aircraft and vehicles. 

2

A runway incursion is any occurrence in the airport runway involving an aircraft, vehicle, 

person, or object on the ground that creates a collision hazard or results in a loss of required 

separation between two aircraft during takeoff or landing. 
Appendix II

Airport Surface Detection Equipment - 

Model X Case Illustration

Page 32 GAO-05-11 Air Traffic Control

Figure 2: Airport Surface Detection Equipment - Model X

Status In October 2003, FAA commissioned ASDE-X at Mitchell International 

Airport in Milwaukee, Wisconsin, for use in the national airspace system. 

ASDE-X came in close to its original schedule and cost baselines. The 

ASDE-X system was approximately 5 months over its original schedule 

baseline, but maintained its original performance baselines. In June 2002, 

FAA approved $80.9 million in additional funding to add ASDE-X at 7 

additional sites. (See table 2.) FAA is currently scheduled to deploy ASDEX at 25 U.S. airports over the next 4 years and to update existing surface 

detection systems (i.e., ASDE-3) at 9 other facilities. FAA plans to introduce 

an upgraded ASDE-X system at T.F. Green Airport in Providence, Rhode 

Island, with deployment tentatively slated for the 4th quarter of 2004. FAA 

is also investigating whether to add ASDE-X at 25 airports that use ASDE-3 

and Airport Movement Area Safety Systems.

Tower display

Radar sensor

Fusion platform/

Display processor

ASR/SSR sensor

Multilateration sensor

Source: FAA.
Appendix II

Airport Surface Detection Equipment - 

Model X Case Illustration

Page 33 GAO-05-11 Air Traffic Control

Table 2: Cost and Schedule Estimate Changes to ASDE-X 

Source: GAO presentation of FAA data.

a

Includes 25 operational ASDE-X sites, 4 support systems, and 1 ASDE-3 upgrade.

b

Includes 7 ASDE-3 site upgrades. 

c

The October 2003 cost estimate includes a $5 million congressional addition for Dulles Airport.

d

Although the last approved baseline included the 2007 date for last deployment, internal and external 

reprogramming for other high-priority activities and budget decrements in fiscal years 2004 and 2005 

will slip the last deployment to fiscal year 2009. The ASDE-X program office is preparing a baseline 

management notice to adjust the baseline. 

FAA Faced Fewer 

Challenges in 

Approving ASDE-X 

Of the five systems we reviewed, FAA faced fewer schedule and cost 

challenges in approving ASDE-X for safe use in the national airspace 

system. This is partly because FAA included stakeholders early and 

throughout the approval process and because of the strong technical 

expertise of its managers. The ASDE-X program office brought in 

stakeholders, including maintenance technicians and air traffic controllers, 

beginning with the concept of operations phase and continued their 

stakeholder involvement through the requirements-setting, design-anddevelopment, and test-and-evaluation phases and then continued 

involvement throughout the deployment phase. For example, FAA obtained 

the input of controllers and technicians at the beginning of the approval 

process, which helped to ensure that ASDE-X requirements were set at 

appropriate levels and not overspecified or underspecified. Stakeholders 

pointed toward the strong technical expertise of the program’s managers as 

a reason for the appropriate specification of ASDE-X’s requirements. In 

addition, FAA brought ASDE-X stakeholders together at technical meetings 

to provide input on ASDE-X design and development, which allowed the 

ASDE-X program office to design a system that met requirements and 

incorporated stakeholders’ needs. 

Dollars in millions

Baseline/Cost 

estimate year

Estimated 

development 

costs 

Initial operating 

capability 

Full operating 

capability 

September 2001 

(baseline)

$424.3a May 2003 2007

June 2002 

(upgrade)

80.9b September 2004 2005

October 2003

(in-service decision)

510.2c October 2003 2007d
Appendix II

Airport Surface Detection Equipment - 

Model X Case Illustration

Page 34 GAO-05-11 Air Traffic Control

However, FAA did experience some challenges in approving ASDE-X. In 

response to Congress’ desire to deploy the system quickly, FAA attempted 

to accelerate ASDE-X’s approval. However, FAA experienced problems in 

accelerating the approval when it awarded the contract before all 

requirements had been finalized. 

Table 3 shows the major phases and time frames associated with the ASDEX approval process. 

Table 3: ASDE-X Ground System Approval Timeline

Phase Date

Concept of operations May 1998

Requirements setting

Final requirements document September 1999

Contract award (signed) November 2000

Design and development 

Planned human factors requirements February 2001

Critical design review April 2001

Baseline change June 2002

Underdeveloped radars July 2002

Test and evaluation

Development test March 2003

Operational test and evaluation May 2003

Independent operational test and evaluation August 2003

Operational readiness October 2003

Commissioning October 2003

Source: GAO presentation of FAA data.
Page 35 GAO-05-11 Air Traffic Control

Appendix III

Controller-Pilot Data Link Communications 

Case Illustration ApendxiI

Background CPDLC will allow pilots and controllers to transmit digital data messages 

directly between FAA ground automation computers and suitably equipped 

aircraft. (See fig. 3.) CPDLC is a new way for controllers and pilots to 

communicate that is analogous to e-mail. The pilot can read the message 

displayed on a screen in the cockpit and respond to the message with the 

push of a key. In the future, this will alleviate frequency congestion 

problems and increase controller efficiency. One of the most important 

aspects of this technology is its intended reduction of operational errors 

from misunderstood instructions and readback errors. The initial phase 

(Build 1) consisted of four services: initial contact, altimeter1

 setting, 

transfer of communication, and predefined instructions via menu text. The 

CPDLC program will ultimately develop additional capabilities in an 

incremental manner through further development stages. Originally, Build 

1 was to be followed by Build 1A, which was designed to increase the 

CPDLC message set and include assignment of speeds, headings, and 

altitudes as well as a route clearance function. 

1

An altimeter is an instrument for measuring altitude. 
Appendix III

Controller-Pilot Data Link Communications 

Case Illustration 

Page 36 GAO-05-11 Air Traffic Control

Figure 3: Controller-Pilot Data Link Communications

Status CPDLC was commissioned for initial daily use by controllers at Miami on 

October 7, 2002. This completed the stage called Build 1, which included 

four services. American Airlines is the CPDLC launch airline with about 25 

aircraft operating in the Miami Center airspace. Further deployment of 

CPDLC has been deferred until about 2009 after the Joint Resources 

Council did not approve the program in April 2003. The council made this 

decision because it believed that the benefits of CPDLC did not outweigh 

the costs. A number of factors contributed to this decision. First, FAA had 

concerns about how quickly aircraft would install the new airborne 

equipment. Second, the approved program baseline was no longer valid as 

Build 1A investment costs had increased from $114.5 million to $181.7 

million, while the number of locations decreased from 20 to 8 as shown in 

table 4. Third, CPDLC would add $83 million to the operations account.

Source: Department of Transportation, Inspector General.

Ground network

Air traffic controllers

Data link message

Service provider
Appendix III

Controller-Pilot Data Link Communications 

Case Illustration 

Page 37 GAO-05-11 Air Traffic Control

Table 4: Cost and Schedule Estimate Changes to CPDLC 

Source: GAO presentation of FAA data.

a

CPDLC Build 1 costs were $52.2 million.

b

FAA did not approve this cost estimate. 

For fiscal year 2005, program officials requested $3 million for CPDLC. 

According to FAA, this amount would be suitable for shutdown of CPDLC 

at Miami, closeout of Build 1, and alternatives analysis for a follow-on 

program. The contractor, ARINC, had been providing messaging service for 

Miami at no cost. However, the contract for this free service expired on 

June 30, 2004. 

Challenges in 

Approving CPDLC

Lack of full coordination between FAA’s aircraft certification and 

acquisition offices, in which there would have been a full understanding of 

all requirements, compromised the schedule and cost of CPDLC. FAA’s 

acquisitions office, in the interest of meeting the original cost and schedule 

estimates, awarded the contract before FAA had a full understanding of 

system requirements, including those of FAA’s aircraft certification office. 

Requirements that specified in detail how the air and ground equipment 

would operate together were not yet completed prior to award of the Build 

1A contract. The addition of CPDLC hardware and software requirements 

increased costs by $26 million, 39 percent of CPDLC’s Build 1A 

development cost growth. In addition, other system requirement changes 

after contract award increased CPDLC’s baseline development cost 

estimate by another $15 million. In total, these requirement additions 

increased costs by $41 million, almost 61 percent of the total cost increases 

associated with CPDLC Build 1A. (See tables 5, 6, and 7 for timelines of 

CPDLC’s ground system approval and aircraft equipment certification.)

Dollars in millions

Baseline/Cost 

estimate year

Estimated 

development 

costsa

Initial operational 

capability - Build 1

Initial operational

capability - Build 1A

Locations

(after Build 1A - 

completion)

1999 (Build 1A) $114.5 June 2002 June 2005 20 

April 2003b 181.7 October 2002 Undetermined 8
Appendix III

Controller-Pilot Data Link Communications 

Case Illustration 

Page 38 GAO-05-11 Air Traffic Control

Table 5: CPDLC Ground System Approval Timeline (Build 1)

Source: GAO presentation of FAA data.

Table 6: CPDLC Ground System Approval Timeline (Build 1A)

Source: GAO presentation of FAA data.

a

Program has been deferred since completion of the investment analysis.

Phase Date 

Concept of operations (initial) October 1991

Requirements setting

Final requirements document October 1998; revised April 2003

Contract award January 1999

Design and development 

Critical design review September 2000

Test and evaluation

Development test February 2002

Operational test December 2001

Independent operational test and evaluation Early assessment – March 2003

Initial operating capability October 2002

Operational readiness October 2002

Commissioning (Build 1) October 2002

Phase Date 

Concept of operations (initial) October 1991

Requirements setting

Final requirements document November 2002

Investment analysisa July 2003
Appendix III

Controller-Pilot Data Link Communications 

Case Illustration 

Page 39 GAO-05-11 Air Traffic Control

Table 7: CPDLC Aircraft Equipment Certification Timeline 

Source: GAO presentation of FAA data.

Phase Date 

Concept of operations (initial) October 1991

Requirements setting

Certification plan (American Airlines) August 2000

Design and production approval May 2001

Installation approval May 2001

Operational approval September 2002
Page 40 GAO-05-11 Air Traffic Control

Appendix IV

Local Area Augmentation System Case 

Illustration ApendxiIV

Background LAAS is a precision approach and landing system that will augment the 

Global Positioning System (GPS) 1

 to broadcast highly accurate information 

to aircraft on the final phases of a flight. LAAS is being developed 

specifically to provide augmentation to GPS satellites to support Category 

I, II, and III precision approach and landing capability2

 to aircraft operating 

within a 20- to 30-mile radius of an airport. LAAS approaches are to be 

designed to avoid obstacles, restricted airspace, noise-sensitive areas, or 

congested airspace. In addition, a single LAAS ground station is to be 

capable of providing precision approach capability to multiple runways.

LAAS has both ground and air components. LAAS ground components 

include four or more GPS reference receivers, which monitor and track 

GPS signals; very high frequency transmitters for broadcasting the LAAS 

signal to aircraft; and ground station equipment, which generates precision 

approach data and is housed at or near an airport. (See fig. 4.) LAAS users 

will have to purchase aircraft equipment to take advantage of the system’s 

benefits. 

1

GPS is a space-based, radio-navigation system consisting of a constellation of satellites and 

a network of ground stations used for monitoring and control. A minimum of 24 GPS 

satellites orbit the Earth at an altitude of approximately 11,000 miles, providing users with 

accurate information on position, velocity, and time of a GPS-equipped object, such as an 

aircraft, anywhere in the world and in all weather conditions.

2

Category I precision approach has a 200-foot ceiling/decision height and visibility of onehalf mile. Category II precision approach has a 100-foot ceiling/decision height and visibility 

of one-quarter mile. Category III precision approach and landing has a decision height less 

than 100 feet down to the airport surface. 
Appendix IV

Local Area Augmentation System Case 

Illustration

Page 41 GAO-05-11 Air Traffic Control

Figure 4: LAAS Infrastructure

Status FAA’s fiscal year 2005 budget request eliminated funding for LAAS, which is 

being moved from the acquisition program into a research and 

development effort. LAAS was slated for a 2006 rollout, but the target has 

now been deferred until at least 2009. FAA officials said they will 

reconsider national deployment when more research results are 

completed. 

Before FAA decided to suspend funding for LAAS in fiscal year 2005, the 

LAAS program office was negotiating with Honeywell to develop a plan for 

determining how to meet the integrity requirements for the LAAS Category 

I system. According to FAA officials, the LAAS program office will use the 

$18 million remaining in fiscal year 2004 to continue the LAAS Integrity 

Panel for developing the LAAS Category I system, to validate LAAS 

Category II/III requirements, and to solve radio frequency interference 

issues. The $18 million will last through 2005, and FAA’s goal is to meet 

LAAS integrity requirement by September 2005. Because of the budget cuts 

in fiscal year 2005, the LAAS program office will not be developing a 

Category II/III prototype.

As shown in table 8, the LAAS Category I system was initially expected to 

be operational in 2002. However, FAA was unable to meet the milestone, 

primarily due to development and integrity requirement issues. According 

to FAA officials, the research needed to validate the integrity requirement 

GPS

receiver

VHF data broadcast

GPS

receiver

GPS satellites

GPS receiver

GPS receiver

VHF data broadcast

LAAS ground facility

Source: FAA.
Appendix IV

Local Area Augmentation System Case 

Illustration

Page 42 GAO-05-11 Air Traffic Control

of LAAS Category I is scheduled to be completed by September 2005. If 

funds are fully restored in fiscal year 2005, FAA officials said that a LAAS 

Category I system can be developed and deployed by fiscal year 2009.

Table 8: Cost and Schedule Estimate Changes to LAAS 

Source: GAO presentation of FAA data.

FAA Faced Challenges 

in Approving LAAS 

FAA faced a number of challenges in approving LAAS for safe use in the 

national airspace system, including (1) its inability to meet LAAS’ integrity 

requirement, (2) not always communicating with the contractor about what 

was required to satisfy LAAS ground system requirements, and (3) 

accelerating the LAAS schedule by setting milestones before designing the 

system. 

According to Honeywell officials, meeting the integrity requirement has 

been perhaps the most difficult part of approving LAAS for safe use in the 

national airspace system. Under FAA’s integrity requirement for LAAS, the 

system must alert the pilot with timely warnings when it should not be 

used. However, FAA has not been able to develop a solution to meet this 

requirement because it has not been able to prove that the system is safe 

during solar storms. According to FAA officials, one of the reasons that 

FAA has not been able to develop a solution to meet this requirement is that 

a solar storm’s effect on the ionosphere has not been modeled. The 

modeling is scheduled for completion in September 2004, and it will be 

used to design a monitor for ionosphere anomalies that could be developed 

and deployed by fiscal year 2009. 

FAA also did not always communicate with the contractor about what was 

required to satisfy LAAS ground system requirements. Initially, FAA was in 

a partnership with industry, including Honeywell and others, to develop a 

LAAS Category I precision approach and landing system, which has a 200-

foot ceiling height and one-half mile visibility. FAA partnered with industry 

Dollars in millions

Baseline/Cost 

estimate year

Estimated 

development 

costs

Initial operating 

capability

Full operating 

capability

January 1998 (baseline) $530.1 2002 To be determined

September 1999 696.1 2001 To be determined
Appendix IV

Local Area Augmentation System Case 

Illustration

Page 43 GAO-05-11 Air Traffic Control

to develop LAAS because FAA would have to pay industry only if industry 

achieved preset milestones, such as an analysis of the LAAS system 

integrity requirement. However, the partnership was not able to develop a 

system that FAA believed would operate safely in the national airspace 

system. Consequently, FAA decided to acquire LAAS on its own. In April 

2003, FAA awarded a contract to Honeywell to develop a LAAS Category I 

precision approach and landing system. At the time the contract was 

awarded, FAA believed that 80 percent of the LAAS was developed and met 

its ground system requirements based on a review of documents. However, 

5 months later, after further review, FAA discovered that only about 20 

percent of development was complete. Nevertheless, Honeywell believes it 

met 80 percent of the LAAS requirements. Both parties attribute the 

disagreement to lack of communication about what was needed to satisfy 

the LAAS ground system requirements. In fiscal year 2005, FAA decided to 

suspend funding and placed LAAS into its research and development 

program due to a lack of software development and the inability of the 

system to meet the integrity requirement. According to FAA officials, the 

research needed to validate the integrity requirement of LAAS Category I is 

scheduled to be completed by September 2005. If funds are fully restored in 

fiscal year 2005, FAA believes that a LAAS Category I system can be 

developed and deployed by fiscal year 2009. 

FAA also experienced challenges in approving LAAS because it accelerated 

the schedule in 1998 to meet system milestones before completely 

designing the system and developing a solution for meeting the LAAS 

integrity requirement. FAA originally planned to deploy LAAS in 2002 but 

had to subsequently delay deployment to 2006 because of additional 

development work, evolving requirements, and unresolved issues regarding 

how the system would be approved. Lack of a solution for verifying that its 

integrity requirement had been met and incomplete software development 

were significant approval issues facing the LAAS program.

Table 9 shows the major phases and time frames for approving the LAAS 

ground system. 
Appendix IV

Local Area Augmentation System Case 

Illustration

Page 44 GAO-05-11 Air Traffic Control

Table 9: LAAS Ground System Approval Timeline

Source: GAO presentation of FAA and RTCA data.

Certification of LAAS 

Aircraft Equipment 

Has Been Affected by 

Delays in Ground 

System Approval 

LAAS aircraft equipment received design and production approval in 

August 2004. It still awaits installation approval. (See table 10.) Because 

LAAS’ aircraft and ground components are linked, certification of LAAS 

aircraft equipment has been affected by delays occurring during ground 

system approval. For example, according to aviation industry officials, 

requirement additions on LAAS’ ground system led to requirement 

additions on LAAS’ aircraft equipment. According to aviation industry 

officials, the addition of requirements to the ground system increased the 

cost and time to develop aircraft equipment, which changed the calculation 

for industry about whether developing LAAS aircraft equipment was a 

worthwhile investment and discourages future investment in aircraft 

equipment that will modernize the national airspace system.

Phase Date

Concept of operations (initial) 1992 

Requirements setting

RTCA performance standards September 1998 

Creation of LAAS Integrity Panel 1996

Establishment of LAAS government industry 

partnership

1999 

Rebaseline #1 September 1999 

Integrity requirement concerns identified December 2001

Requirements document final June 2002 

LAAS cost estimate change (Category I only) April 2002 

Contract award April 2003 

Design and development 

Software development issues identified September 2003 

Critical design review Not complete

Test and evaluation

Development test Not complete

Operational test and evaluation Not complete

Independent operational test and evaluation Not complete

Operational readiness Not complete

Commissioning/Initial operating capability Not complete 
Appendix IV

Local Area Augmentation System Case 

Illustration

Page 45 GAO-05-11 Air Traffic Control

FAA’s Aircraft 

Certification Office 

Needs to Coordinate 

Better with 

Acquisitions Offices

FAA’s aircraft certification office completed the design and production 

approval of LAAS aircraft equipment without coordinating with the offices 

responsible for acquisition to determine the consequences of certifying 

aircraft equipment before approval of the associated ground system. 

According to an FAA official, once the aircraft certification office has given 

design and production approval to the LAAS aircraft equipment, it is not 

possible to make a change to the requirements for the aircraft equipment so 

that they are better integrated with the associated LAAS ground system. 

Consequently, LAAS ground system developers may have to make more 

costly and time-consuming changes to the ground system than would have 

been necessary if the aircraft certification and acquisitions offices had 

coordinated their efforts.

Table 10: LAAS Aircraft Equipment Certification Timeline 

Source: GAO presentation of FAA data.

a

FAA first approved the use of GPS for aviation navigation in 1993, so new aircraft equipment that uses 

GPS did not require a new operational approval.

Phase Date

Concept of operations (initial) 1992 

Requirements setting

LAAS minimum operating performance 

standards 

1995 to 2001

LAAS technical standard order development March 2003

Design and production approval August 2004

Installation approval Not complete

Operational approval Not requireda
Page 46 GAO-05-11 Air Traffic Control

Appendix V

Standard Terminal Automation Replacement 

System Case Illustration ApendxiV

Background STARS is a joint Department of Transportation, FAA, and Department of 

Defense (DOD) program established under 31 U.S.C. 1535, the Economy 

Act, as amended, to replace aging FAA and DOD legacy terminal 

automation systems with state-of-the-art terminal ATC systems. The joint 

program is intended to avoid duplication of development and logistic costs 

while providing easier transition of controllers between the civil and 

military sectors. Civil and military air traffic controllers across the nation 

are using STARS to direct aircraft near major airports. FAA’s goal for 

STARS is to provide an open, expandable terminal automation platform 

that can accommodate future air traffic growth and allow for the 

introduction of new hardware- and software-based tools to promote safety, 

maximize operational efficiency, and improve controllers’ productivity. 

FAA believes that STARS will facilitate efforts to optimally configure the 

terminal airspace around the country, exchange digital information 

between pilots and controllers, and introduce new position and 

surveillance capabilities for pilots. (See fig. 5.)

Figure 5: Standard Terminal Automation Replacement System

Source: FAA.
Appendix V

Standard Terminal Automation Replacement 

System Case Illustration

Page 47 GAO-05-11 Air Traffic Control

Status In June 2003, FAA first commissioned STARS for use at the Philadelphia 

International Airport in Pennsylvania. Currently, STARS is fully operational 

at 25 FAA terminal radar control facilities and 17 DOD facilities. Under the 

Air Traffic Organization’s new business model of breaking large and 

complex programs into smaller phases to control cost and schedule, 

STARS is a candidate for further deployment to about 120 FAA terminal 

radar control facilities. As shown in table 11, in April 2004, FAA changed 

STARS’ cost and schedule estimates for the third time and now estimates 

that it will cost $1.46 billion to deploy STARS at the 50 most important 

terminal radar control facilities that provide air traffic control services to 

20 of the nation’s top 35 airports. The original baseline in February 1996 

was $940 million for 172 systems. The April 2004 estimate is an increase of 

about $500 million for 122 fewer systems (i.e., over 70 percent less) than 

originally planned.

Table 11: Cost and Schedule Estimate Changes to STARS 

Source: GAO presentation of FAA data.

a

This estimate includes development costs only and does not include technology refresh and terminal 

automation enhancement.

b

The February 1996 baseline included limited human factors evaluations and a basic commercial offthe-shelf configuration. 

c

The April 2004 baseline occurred after STARS’ commissioning in June 2003 in Philadelphia, 

Pennsylvania. 

FAA Faced Challenges 

in Approving STARS 

FAA faced challenges in approving STARS. Although controllers and 

technicians were involved in developing requirements for STARS prior to 

the 1996 contract award to Raytheon, the original approved acquisition 

plan provided only limited human factors evaluation from controllers and 

technicians during STARS’ design and development phase. The acquisition 

approach was to employ a commercial off-the-shelf system with limited 

Dollars in billions

Baseline/Cost 

estimate year

Estimated 

development costsa

Projected date for 

first deployment of 

STARS

Projected date for 

last deployment 

of STARS 

Number of FAA systems 

receiving STARS

February 1996 b $0.94 1998 2005 172

October 1999 1.40 2002 2008 188

March 2002 1.33 2002 2005 73

April 2004c 1.46 2003 2008 50
Appendix V

Standard Terminal Automation Replacement 

System Case Illustration

Page 48 GAO-05-11 Air Traffic Control

modifications, and the competition was limited to companies with already 

operational ATC systems. In 1997, FAA controllers, who were accustomed 

to using the older equipment, began to voice concerns about computerhuman interface issues that could hamper their ability to monitor air 

traffic. For example, the controllers noted that many features of the old 

equipment could be operated with knobs, allowing controllers to focus on 

the screen. By contrast, the STARS commercial system was menu-driven 

and required the controllers to make several keystrokes and use a 

trackball, diverting their attention from the screen. The maintenance 

technicians also identified differences between STARS and its backup 

system that made monitoring the system less efficient. For example, the 

visual warning alarms and color codes identifying problems were not 

consistent between the two systems. In 1997, FAA, the National Air Traffic 

Controllers Association, the Professional Airways System Specialists, and 

Raytheon formed a team to deal with these computer-human interface 

issues. The team identified 98 air traffic and 52 airway facilities computerhuman interface enhancements to address these issues.

FAA and Raytheon restructured the contract to address the technicians’ 

and controllers’ concerns. According to FAA, not involving controllers and 

maintenance technicians caused FAA to revise its strategy for approving 

STARS, which FAA estimates added $500 million and 3 years to the 

schedule. The original STARS cost estimate of $940 million included limited 

human factors evaluations and the use of a basic commercial off-the-shelf 

configuration. This acquisition strategy was replaced by an incremental 

development strategy that incorporated up front the majority of human 

factors considerations and additional functionality that were not included 

in the original cost estimate. This new acquisition strategy added years to 

the development schedule and significantly increased the system’s 

requirements specifications. These additional requirements resulted in 

both cost and schedule growth. FAA’s own guidance showed that limiting 

human factors evaluations will result in higher costs and schedule delays. 

Initially, it is more expensive (in terms of time and funding) to deal with 

human factors considerations than to ignore them. However, an initial 

human factors investment pays high dividends, in terms of costs and 

schedule, in later stages of acquisition when changes are more costly and 

difficult to make. 

FAA also experienced challenges in approving STARS, partly, because of 

aggressive scheduling. FAA’s approach to approving STARS was oriented to 

rapid deployment to meet critical needs. To meet these needs, FAA 

compressed its original development and testing schedule from 32 months 
Appendix V

Standard Terminal Automation Replacement 

System Case Illustration

Page 49 GAO-05-11 Air Traffic Control

to 25 months. This acceleration in schedule left only limited time for human 

factors evaluations and not enough time for involvement of controllers and 

maintenance technicians. 

Table 12 shows the major phases and time frames associated with the 

STARS approval process. 

Table 12: STARS Ground System Approval Timeline

Source: GAO representation of FAA data.

Phase Date

Concept of operations (initial) 1993

Requirements setting

Requirements setting occurred 1994

Contract award September 1996

Design and development

System design review December 1996

Human factors issues identified 1997

STARS baseline change October 1999

Test and evaluation

Development test (Philadelphia, Full Stars-2 

Plus)

January 2002

Operational test and evaluation (Philadelphia) August 2002

Independent operational test and evaluation 

(Philadelphia)

January 2003

Operational readiness/Commissioning 

(Philadelphia)

June 2003
Page 50 GAO-05-11 Air Traffic Control

Appendix VI

Wide Area Augmentation System Case 

Illustration ApendxiVI

Background WAAS is a GPS-based navigation and landing system. According to FAA, 

WAAS is to improve safety by providing precision guidance to aircraft in all 

phases of flight at thousands of airports and landing strips, including 

runways, where there is no ground-based landing capability. To use WAAS 

for navigation, an aircraft must be equipped with a certified WAAS receiver 

that is able to process the information carried by GPS and WAAS 

geostationary satellite signals. Pilots are able to use this information to 

determine their aircrafts’ time and speed, and latitude, longitude, and 

altitude positions. WAAS currently consists of a network of 25 ground 

reference stations, 2 leased geostationary satellites, 2 master stations, and 

4 uplink (ground earth) stations. The ground reference stations are 

strategically positioned across the United States to collect GPS satellite 

data. (See fig. 6.) WAAS is designed to improve the accuracy, integrity, and 

availability of information coming from GPS satellites and to correct signal 

errors caused by solar storms, among other things. 

Figure 6: WAAS Architecture

GPS satellites

Geostationary

satellite

Geostationary

satellite

Reference station Ground earth

Master station station

Source: FAA.
Appendix VI

Wide Area Augmentation System Case 

Illustration

Page 51 GAO-05-11 Air Traffic Control

FAA expects that WAAS will improve the national airspace system by (1) 

increasing runway capability; (2) reducing separation standards that allow 

increased capacity in a given airspace without increased risk; (3) providing 

more direct en route flight paths; (4) providing new precision approach 

services; (5) reducing the amount of and simplifying equipment on board 

aircraft; (6) saving the government money due to the elimination of 

maintenance costs associated with older, more expensive ground-based 

navigation aids; and (7) providing vertical guidance in all phases of flight to 

improve safety. 

Status In July 2003, FAA commissioned WAAS to provide initial operating 

capability for 95 percent of the United States. In July 2003, the first of the 

LPV1

 approaches were provided whereby pilots could safely descend to a 

250-foot decision height.2 As of August 2004, there were about 20 LPV 

landing procedures published for WAAS. With over 4,000 runways needing 

them, much work still needs to be done to fully utilize the WAAS capability. 

FAA expects to have WAAS available in the rest of the country, with the 

exceptions of a few parts of Alaska, by the end of 2008 when it completes 

the addition of 13 ground reference stations and 2 leased geostationary 

satellites. WAAS is not scheduled to achieve full (Category I) operating 

capability, the final phase of WAAS when pilots will be able to use it to 

navigate as low as 200 feet above the runway, until the 2013-2019 time 

frame.3

As shown in table 13, FAA changed WAAS’ cost and schedule estimates for 

the third time in May 2004. According to FAA, the reasons for the May 2004 

rebaselining were that the system was not able to achieve full Category 1 

capability and because of FAA internal and congressional budget cuts. 

Under the May 2004 baseline, FAA estimates that WAAS development costs 

will be about $2.0 billion, which is $1.5 billion higher than the 1994 

estimated development costs. Also, FAA has not yet met some of its 

original performance goals, such as providing pilots with the ability to 

1

LPV is an acronym with no specific definition today but once stood for Lateral Precision 

Vertical.

2

A ceiling or decision height is the height above the Earth’s surface to the lowest layer of 

clouds or obscuring phenomena.

3

Category I precision approach has a 200-foot ceiling/decision height and visibility of onehalf mile. 
Appendix VI

Wide Area Augmentation System Case 

Illustration

Page 52 GAO-05-11 Air Traffic Control

navigate as low as 200 feet above the runway. According to FAA, WAAS 

cannot easily achieve Category I as a single frequency system because the 

error sources caused by solar storms are difficult to correct without the use 

of a second civil aviation frequency in space, which is the responsibility of 

the Department of Defense. FAA, realizing the difficulty and risk associated 

with developing a single frequency Category I system, decided to wait and 

leverage the benefits of the White House policy to include the second civil 

frequency on the GPS satellite network. According to FAA, budget cuts and 

the decision to wait until the second civil frequency is placed on the GPS 

constellation have caused it to extend the timeline for reaching WAAS’ full 

Category I operating capability to between 2013 and 2019. 

Table 13: Cost and Schedule Baseline Changes to WAAS 

Source: GAO presentation of FAA data.

a

The September 1999 estimate for WAAS development does not include $1.3 billion in satellite service 

acquisition through 2020. In earlier estimates, satellite service acquisition costs were included in the 

cost of operating WAAS, not developing WAAS.

b

The May 2004 estimate for WAAS development does not include $1.3 billion in satellite service 

acquisition through 2028. In earlier estimates, satellite service acquisition costs were included in the 

cost of operating WAAS, not developing WAAS.

FAA Faced Challenges 

in Approving WAAS

FAA faced challenges in approving WAAS ground and satellite components 

for use in the national airspace system, partly because of FAA’s accelerated 

scheduling, lack of effective coordination between its aircraft certification 

office and acquisitions office, and technical challenges which resulted in a 

delay meeting the integrity requirement. FAA’s challenges in approving 

WAAS began in 1994 when FAA accelerated the implementation of 

milestones, including moving up the commissioning of WAAS by 3 years. 

FAA originally planned to commission WAAS in 2000; however, at the 

urging of government and aviation industry groups in the 1990s, it decided 

to change WAAS’ commissioning date to 1997. FAA tried to develop, test, 

Dollars in millions

Baseline year

Estimated 

development 

costs

Initial operating 

capability 

Full operating 

capability 

1994 $509 June 1997 December 2000

January 1998 1,007 August 1999 December 2001

September 1999 1,683a September 2000 December 2006

May 2004 2,036b July 2003 2013-2019
Appendix VI

Wide Area Augmentation System Case 

Illustration

Page 53 GAO-05-11 Air Traffic Control

and deploy WAAS within 28 months, despite the fact that software 

development alone was expected to take 24 to 28 months. FAA also set 

system milestones before completing the research and development 

required to prove the system’s capability. Although FAA attempted to 

accelerate the implementation of WAAS, it wasn’t until July 2003, 6 years 

later, that it was able to commission WAAS with initial operating capability. 

Lack of full involvement between FAA’s aircraft certification members and 

the rest of the integrated product team contributed to delays in approving 

WAAS. For example, although an integrated product team, which included 

representatives from aircraft certification and acquisition offices, was 

developing WAAS, it was not until September 1999, when the aircraft 

certification office became fully involved, that FAA recognized (1) the 

difficulty of meeting the integrity requirement—that WAAS must alert the 

pilot in a timely manner when the system should not be used—and (2) it did 

not have the technical expertise needed. According to FAA officials, the 

reason coordination did not occur was because the two offices had 

competing priorities, such as the day-to-day aircraft equipment 

certification activities not associated with the development of a new ATC 

system. This situation may have developed because FAA’s aircraft 

certification organization is more accustomed to being involved after a 

project is developed, rather than actively participating throughout project 

development. 

The need to meet WAAS’ integrity requirement also hampered FAA’s ability 

to approve WAAS for safe use in the national airspace system. In December 

1999, FAA found that WAAS did not meet the agency’s integrity requirement 

for precision approaches, and FAA recognized that it did not have the 

technical expertise required to resolve the issue. Therefore, in 2000, FAA 

established a team of satellite navigation experts, which was referred to as 

the WAAS Integrity Performance Panel and included representatives from 

the MITRE Corporation, Stanford University, Ohio University, and the Jet 

Propulsion Laboratory. Developing a solution to prove that the WAAS 

design met the integrity requirement added about 2 years and 4 months to 

the approval process and contributed to WAAS’ cost growth. All of these 

challenges contributed to a 6-year delay in WAAS’ commissioning and a 

$1.5 billion increase in its estimated total development costs through 2028, 

exclusive of operating and maintaining geostationary satellites, which were 

not part of WAAS’ original 1994 baseline. Table 14 shows the major phases 

and time frames associated with approving WAAS’ ground system.
Appendix VI

Wide Area Augmentation System Case 

Illustration

Page 54 GAO-05-11 Air Traffic Control

Table 14: WAAS Ground System Approval Timeline

Source: GAO presentation of FAA and RTCA data.

FAA Did Not 

Experience Major 

Challenges in 

Certifying the Aircraft 

Equipment of WAAS

In contrast to the challenges that it encountered during the approval of the 

WAAS ground system, FAA did not encounter major challenges with the 

certification of WAAS aircraft equipment, primarily because FAA had an 

up-front approval agreement with one of the first applicants, United Parcel 

Service Aviation Technology, through the creation and approval of a safety 

plan and a project-specific certification plan. Table 15 shows the major 

phases and time frames associated with certifying the aircraft equipment of 

WAAS. Currently, WAAS GPS receivers have been certified and are 

available for use. 

Phase Date

Concept of operations June 1992

Requirements setting

Operational requirements document June 1994

Original contract award August 1995

Current contract award May 1996

Design and development

Critical design review December 1997

Test and evaluation

Development test (failed) December 1999

WAAS Integrity Performance Panel formed January 2000

Development test (passed) September 2002

Operational test and evaluation March 2003

Operational readiness/Commissioning July 2003
Appendix VI

Wide Area Augmentation System Case 

Illustration

Page 55 GAO-05-11 Air Traffic Control

Table 15: WAAS Aircraft Equipment Certification Timeline

Source: GAO presentation of FAA data.

a

FAA first approved the use of GPS for aviation navigation in 1993; therefore, new aircraft equipment 

that use GPS did not require a new operational approval.

Phase Date

Concept of operations June 1992

Requirements setting

RTCA WAAS minimum operational 

performance standards (four major revisions)

1994 to November 2001

WAAS technical standard orders (four major 

revisions)

May 1998 to September 2002

Design and production approval

Data submitted for supplemental type 

certificate and technical standard order 

authorization

June 2, 2003

Technical standard order authorization (United 

Parcel Service Aviation Technology)

June 13, 2003

Installation approval – Type 

certificate/Supplemental type certificate (United 

Parcel Service Aviation Technology)

June 27, 2003

Operational approval Not requireda
Page 56 GAO-05-11 Air Traffic Control

Appendix VII

GAO Contacts and Staff Acknowledgments ApendxiVI

GAO Contacts Katherine Siggerud, (202) 512-2834 or siggerudk@gao.gov

Tammy Conquest, (202) 512-5234 or conquestt@gao.gov

Staff 

Acknowledgments

In addition to the individuals named above, other key contributors to this 

report were Geraldine Beard, Gerald Dillingham, Seth Dykes, David 

Hooper, Kevin Jackson, Gregg Justice III, Donna Leiss, and Kieran 

McCarthy.

(540057)
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