Report to Congressional Committees

United States Government Accountability Office

GAO 

AVIATION AND THE 

ENVIRONMENT 

FAA’s and NASA’s 

Research and 

Development Plans 

for Noise Reduction 

Are Aligned but the 

Prospects of 

Achieving Noise 

Reduction Goals Are 

Uncertain

February 2008 

GAO-08-384 
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

February 2008

AVIATION AND THE ENVIRONMENT

FAA’s and NASA’s Research and Development Plans

for Noise Reduction Are Aligned, but the Prospects of 

Highlights of GAO-08-384, a report to Achieving Noise Reduction Goals Are Uncertain 

congressional committees 

Reducing aviation noise is 

important to the efficient operation 

and expansion of the National

Airspace System because 

community opposition to aviation 

noise is a major obstacle to airport

and runway development. Such 

development is needed to help 

address congestion and meet the 

nation’s rapidly growing demand

for air travel. The Federal Aviation

Administration (FAA) and the 

National Aeronautics and Space 

Administration (NASA) have the

primary federal responsibility for 

research and development (R&D) 

on aviation noise. FAA focuses on 

the impacts of aviation noise on

communities, while NASA focuses 

on noise at its source—aircraft 

engines and airframes. Both FAA 

and NASA have set noise reduction 

goals. 

This congressionally requested 

report on aviation noise addresses 

(1) FAA’s and NASA’s R&D plans 

for addressing aviation noise and

the extent to which they are 

aligned and (2) FAA’s and NASA’s 

noise reduction goals and the 

likelihood that these goals will be 

achieved. 

To conduct its work, GAO 

reviewed FAA’s and NASA’s R&D 

planning documents, coordinating 

mechanisms, and research plans 

and interviewed agency officials. In 

addition, aviation industry 

representatives reviewed and 

commented on a draft of this 

report. A draft was provided to

FAA and NASA. Both agencies had 

no comment.

FAA’s and NASA’s R&D plans include a wide range of projects for addressing

aviation noise, and these plans are aligned through partnerships and planning 

and coordinating mechanisms. FAA sponsors aviation noise R&D in areas 

such as aviation noise measurement, aviation noise effects, aviation noise and 

emissions interrelationships, and flight procedures and technologies to 

mitigate the impact of noise on communities. FAA sponsors much of this 

research through partnerships with universities; other federal agencies, 

including NASA; and industry. NASA conducts R&D that can eventually lead 

to new technologies for making substantially quieter aircraft provided that the 

technologies are further developed by industry and integrated into

production-ready aircraft designs. FAA and NASA have aligned their aviation 

noise R&D activities by working with interagency planning and coordinating 

groups to establish objectives for the nation’s aeronautical research and for 

specific research on the environmental impacts of next generation aviation 

technologies. Both agencies also serve on the same aviation research advisory

groups, and the alignment of their aviation noise R&D activities is reflected in 

strategic plans for the National Airspace System that indicates how each 

agency’s R&D efforts will contribute to meeting goals for reducing noise and 

thereby help reduce community opposition to increasing aviation system 

capacity. 

FAA’s and NASA’s noise reduction goals are designed, together, to reduce 

people’s exposure to aviation noise primarily by reducing such noise at its 

source, but the likelihood of achieving these goals is uncertain. Under FAA’s 

targets, the number of people exposed to significant aviation noise—

estimated at 500,000 nationwide—would be reduced by 4 percent a year 

through fiscal year 2012. NASA’s targets, established for the next three 

generations of aircraft, would lead to the entry into service of successively

quieter aircraft by 2015, 2020-2025, and 2030-2035, respectively. The likelihood 

of meeting these targets depends on a number of uncertainties. First, federal 

funding will be needed not only for NASA’s research but also for later-stage 

R&D, which NASA expects others to perform. The administration has 

proposed a 10-year program to support later-stage R&D to demonstrate 

technologies for industry acceptance. But even if funded, the development of 

noise reduction technologies may be limited by concerns about global 

warming, since advances in these technologies could make it more difficult to 

also achieve reductions in aircraft emissions of greenhouse gases. Also 

uncertain is the extent to which manufacturers will integrate newly developed 

technologies into aircraft and engine designs. Finally, it is uncertain whether 

airlines will purchase new aircraft or retrofit existing aircraft with the new 

technologies in sufficient numbers to achieve targeted reductions in exposure 

to aviation noise. Failure to achieve FAA’s and NASA’s noise reduction goals 

could constrain efforts to expand the National Airspace System’s capacity and 

reduce congestion. To view the full product, including the scope 

and methodology, click on GAO-08-384. 

For more information, contact Gerald L. 

Dillingham at (202) 512-2834 or 

dillinghamg@gao.gov. 
Contents 

Letter 1

Results in Brief 4 

FAA and NASA Use Partnerships and Planning and Coordinating 

Mechanisms to Align R&D on Noise Reduction 6 

FAA and NASA Have Established Noise Reduction Technology 

Goals, but R&D Funding Issues and Other Factors Make the 

Achievement of Noise Reduction Goals Uncertain 16 

Agency Comments 22 

Appendix I PARTNER Participants and Projects 23 

Appendix II NASA Letter to GAO 26 

Appendix III GAO Contact and Staff Acknowledgments 27

Tables 

Table 1: AIP and PFC Investments for Noise-Related Purposes for 

Fiscal Years 1982-2007 8 

Table 2: FAA Funds for R&D Efforts in Fiscal Years 1997-2007 10 

Table 3: NASA’s N+X Generation Aircraft Program 18 

Figures 

Figure 1: NASA’s Research Approach Triangle 11 

Page i GAO-08-384 Aviation and the Environment 
Abbreviations 

ADS-B Automatic Dependent Surveillance-Broadcast 

AIP Airport Improvement Program 

CDA Continuous Descent Arrival 

CLEEN Continuous Lower Energy, Emissions and Noise 

dB decibel 

DNL day-night level 

EPN effective perceived noise

FAA Federal Aviation Administration 

ICAO International Civil Aviation Organization 

JPDO Joint Planning and Development Office 

MOU memorandum of understanding 

NAS National Airspace System

NASA National Aeronautics and Space Administration

NextGen Next Generation Air Transportation System 

NRA NASA Research Announcement 

OSTP Office of Science and Technology Policy 

PARTNER Partnership for Air Transportation Noise and Emissions 

Reductions 

PFC passenger facility charge 

R&D research and development 

REDAC Research, Engineering, and Development Advisory 

Committee 

This is a work of the U.S. government and is not subject to copyright protection in the 

United States. The published product may be reproduced and distributed in its entirety 

without further permission from GAO. However, because this work may contain 

copyrighted images or other material, permission from the copyright holder may be 

necessary if you wish to reproduce this material separately. 

Page ii GAO-08-384 Aviation and the Environment 
United States Government Accountability Office

Washington, DC 20548 

February 15, 2008 

The Honorable Mark Udall 

Chairman 

The Honorable Tom Feeney 

Ranking Member 

Subcommittee on Space and Aeronautics 

Committee on Science and Technology 

House of Representatives 

The Honorable Jerry Costello 

Chairman 

The Honorable Thomas Petri 

Ranking Republican Member 

Subcommittee on Aviation 

Committee on Transportation and Infrastructure 

House of Representatives 

Aviation noise continues to be a challenge to the operation and expansion 

of the National Airspace System (NAS). Air traffic has grown steadily over

the past 5 years and is expected to continue growing as more flights are 

required to carry the 1 billion passengers anticipated by 2015. To handle 

the forecasted growth, the Joint Planning and Development Office (JPDO), 

an interagency organization within the Department of Transportation’s 

Federal Aviation Administration (FAA), is working to plan a new air traffic 

management system, the Next Generation Air Transportation System 

(NextGen). Critical objectives for NextGen are to improve the overall 

safety and increase the efficiency of the NAS. Achieving these objectives 

will involve the implementation of new technologies and air traffic control

procedures; airspace redesigns; and infrastructure developments, 

including new or expanded runways and airports. However, community 

opposition to these developments is a major challenge, largely because of

concerns about aviation noise. According to JPDO’s 2007 Concept of 

Operations document, current operational trends show that environmental 

impacts will be the primary constraint on the capacity and flexibility of the 

NAS unless these impacts are managed and mitigated. Legislative 

Page 1 GAO-08-384 Aviation and the Environment 
proposals to reauthorize FAA1

 include a number of provisions designed to 

address aviation noise issues. 

To address aviation noise and its impacts, the federal government follows 

a “balanced approach” recommended by the International Civil Aviation 

Organization (ICAO).2

 This balanced approach recognizes that short-term 

opportunities to mitigate the impacts of noise on communities through 

noise abatement programs, the soundproofing of residences and public 

buildings, and operational restrictions on aircraft should be combined 

with longer-term efforts to reduce aviation noise. Such longer-term efforts 

include reducing noise at its source through more stringent noise 

standards and supporting research and development (R&D) to make 

aircraft quieter, developing and implementing NextGen technologies and 

procedures, and encouraging compatible land use. As part of this balanced

approach, FAA and the National Aeronautics and Space Administration

(NASA) have the principal federal responsibility for R&D to address 

aviation noise. FAA, through its partnerships with universities and through 

JPDO, supports a broad range of research on measuring and reducing the

impacts of noise on communities, while NASA’s research program focuses 

on reducing noise at its source—in aircraft engines and airframes. NASA, 

in partnership with the aircraft and engine manufacturing industry, has 

contributed to a number of advancements in aircraft engine and airframe 

technology that have substantially reduced the amount of noise produced 

by aircraft and may lead to further reductions, depending on the extent to

which current research leads to noise-reducing aircraft engine and 

airframe designs and other factors. FAA and NASA have set technology 

goals for reducing aviation noise. For example, FAA has set a system-level 

goal of a 4 percent yearly reduction in the number of people exposed to 

significant aviation noise. 

You requested that we study noise and other environmental impacts of 

aviation that may fundamentally constrain air transportation in the 21st 

century. In October 2007, we testified before the Subcommittee on 

Aviation, House Transportation and Infrastructure Committee, on the 

impacts of aviation noise on efforts to expand the capacity of airports and 

 1

H.R. 2881 and S. 1300. 

2

ICAO is an advisory organization affiliated with the United Nations that aims to promote

the establishment of international civil aviation standards and recommended practices and 

procedures.

Page 2 GAO-08-384 Aviation and the Environment 
the NAS.3

 This report provides additional information on aviation noise, 

focusing particularly on FAA’s and NASA’s R&D related to this issue and 

on the ability of the two agencies to achieve their respective noise 

reduction goals through their R&D on aviation noise. Specifically, we 

addressed the following questions: 

1. What are FAA’s and NASA’s R&D plans for addressing aviation noise 

and to what extent are these plans aligned? 

2. What are FAA’s and NASA’s noise reduction goals, and what is the 

likelihood that the established goals will be achieved? 

To determine FAA’s and NASA’s aviation noise R&D plans, we reviewed 

FAA and NASA R&D planning documents and other information provided 

by these agencies on their near-term and long-term goals. To determine the

extent to which FAA’s and NASA’s aviation noise-related activities are 

aligned to meet noise reduction goals, we obtained and analyzed 

information on mechanisms in place to coordinate noise R&D activities, 

such as JPDO’s Environmental Working Group and FAA’s Research, 

Engineering, and Development Advisory Committee (REDAC). We also 

compared FAA’s and NASA’s R&D plans to determine whether they are

complementary and in line with JPDO’s and the Executive Office of the

President’s Office of Science and Technology Policy’s (OSTP) plans. We 

also analyzed how the agencies periodically assess the potential for 

synergies or gaps in research activities. In addition, we interviewed agency 

officials on the results of our analyses. To determine FAA’s and NASA’s 

noise reduction goals and the likelihood of meeting those goals, we 

reviewed FAA and NASA R&D planning documents and other information 

provided by the agencies. We also interviewed agency officials to obtain 

their views on the likelihood of meeting noise reduction goals within the 

established time frames. Three external aviation experts reviewed a draft

of this report for accuracy and balance. We conducted this performance 

audit from November 2007 through February 2008 in accordance with 

generally accepted government auditing standards. Those standards 

require that we plan and perform the audit to obtain sufficient, appropriate 

evidence to provide a reasonable basis for our findings and conclusions 

based on our audit objectives. We believe that the evidence obtained 

provides a reasonable basis for our findings and conclusions based on our 

audit objectives. 

 3

GAO, Aviation and the Environment: Impact of Aviation Noise on Communities

Presents Challenges for Airport Operations and Future Growth of the National Airspace

System, GAO-08-216T (Washington, D.C.: Oct. 24, 2007). 

Page 3 GAO-08-384 Aviation and the Environment 
FAA’s and NASA’s R&D plans include a wide range of projects for 

addressing aviation noise, and these activities are aligned through 

partnerships and planning and coordinating mechanisms. FAA sponsors 

aviation noise R&D in a number of areas, including aviation noise 

measurement, the effects of aviation noise, the interrelationships between 

aviation noise and emissions, and flight procedures and technologies that 

can mitigate the impacts of noise on communities. FAA sponsors much of 

this research through partnerships with universities; other federal 

agencies, including NASA; and industry as part of its Partnership for Air 

Transportation Noise and Emissions Reduction (PARTNER) Center of 

Excellence.4

 NASA is the federal agency primarily responsible for 

conducting R&D to reduce the amount of noise produced by aircraft 

engines and airframes. NASA’s aviation noise efforts focus on what NASA 

refers to as “fundamental research”, a stage of the R&D process that takes 

a technology to a point where it can be further matured by manufacturers 

and eventually incorporated into new aircraft or engine designs. These 

technologies have the potential to make the next generations of aircraft 

substantially quieter than today’s aircraft—provided that industry further 

develop the technologies and manufacturers integrate them into 

production-ready aircraft. FAA and NASA have aligned their aviation noise

R&D plans through a number of planning and coordinating mechanisms in 

order to ensure that these plans are complementary and contribute to 

goals for addressing the environmental impacts of aviation, particularly as

these impacts relate to the implementation of NextGen. FAA and NASA 

have participated in planning and establishing objectives for the nation’s 

aeronautical research through OSTP, within the Executive Office of the

President, as well as for specific research to address the environmental 

impacts of NextGen as part of JPDO’s Environmental Working Group. In 

addition, FAA and NASA sit on the advisory board of PARTNER, which 

also includes representatives from the aircraft manufacturing industry, 

airlines, airports, and communities. Furthermore, NASA is a member of 

FAA’s REDAC, and FAA participates in reviews of NASA’s aviation noise 

research program. FAA’s and NASA’s alignment of their aviation noise 

R&D activities is reflected in JPDO’s strategic plans for NextGen, which 

indicate how each agency’s R&D efforts will contribute to meeting goals 

for reducing noise and thereby help to address an impediment to 

increasing the aviation system’s safety and efficiency. 

Results in Brief 

 4

FAA Centers of Excellence are FAA partnerships with universities and affiliated industry 

associations and businesses throughout the country that conduct aviation research in a

number of areas, including advanced materials, aircraft noise and emissions, and 

airworthiness.

Page 4 GAO-08-384 Aviation and the Environment 
In conjunction with their aligned R&D plans, FAA and NASA have set 

noise reduction goals, although the likelihood that these goals will be 

achieved depends on the implementation of noise reduction technologies 

developed through the agencies’ research and other factors. FAA estimates 

that about 500,000 people in the United States are significantly impacted 

by aviation noise, and, under FAA’s goal, the number of people exposed to 

aviation noise would decrease by 4 percent a year through fiscal year 

2012.

5

 NASA’s noise goals, established for the next three generations of 

aircraft, could lead to the entry into service of successively quieter 

aircraft. NASA’s goals include a cumulative reduction6

 in the effective 

perceived noise (EPN)7

 of 32 decibels (dB)—expressed as a noise 

reduction of 32 EPN dB—relative to the current most stringent noise 

standard, for the next generation of aircraft expected to enter service in 

2015. More aggressive NASA goals for the generations of aircraft entering 

service from 2020 through 2025 and from 2030 through 2035 are 

cumulative reductions of 42 EPN dB and 71 EPN dB, respectively, relative

to the standard. NASA’s goals would be achieved if noise reduction is the 

only aim; however, when other factors are considered, such as the need to

reduce aircraft emissions, the noise reductions could be lower. 

NASA officials stress that when NASA’s research ends, it is up to industry 

to develop the technologies further. Thus, aircraft and engine 

manufacturers will then need to integrate the technologies into aircraft 

and engine designs, and there are no guarantees that these additional steps 

will be taken. According to FAA, additional funding is needed to ensure 

the continued development and use of near-term technologies to meet 

noise reduction goals for NextGen. To move noise reduction technologies 

beyond NASA’s stage of development, the House fiscal year 2007 

reauthorization proposal for FAA includes the Continuous Lower Energy, 

Emissions and Noise (CLEEN) initiative, which would create a program 

for the development, maturation, and certification of airframe 

technologies for aircraft over the next 10 years to reduce aviation noise 

 5

This goal is measured by a 3-year moving average for calendar years 2000 through 2002. In

fiscal year 2007, the noise exposure goal was revised from a 1 percent to a 4 percent 

cumulative reduction per year in the number of people exposed to significant aviation 

noise. 

6

The NASA goals are cumulative decreases that are obtained by adding together the 

decreases in an aircraft’s maximum noise levels at take off, flyover, and approach. 

7

EPN is the noise measure used to establish compliance with noise certification standards. 

Page 5 GAO-08-384 Aviation and the Environment 
and emissions.8

 According to FAA, the program, in which NASA will 

participate as an adviser, is intended to accelerate near-term technology 

maturation and to demonstrate to aircraft and engine manufacturers the 

readiness of these technologies for incorporation into new aircraft and 

engine designs. Concern about other environmental problems, such as 

global warming and air quality, may also limit the likelihood of achieving 

FAA’s and NASA’s noise reduction goals, since it will be technologically

challenging to design aircraft with reduced noise while, at the same time, 

achieving the significant reductions in greenhouse gases and other 

emissions that will be required. Furthermore, even if R&D efforts do lead

to next generation aircraft that meet NASA’s noise reduction goals, 

integrating these quieter aircraft into the fleet to the extent that they have

a significant impact on noise reduction will be a challenge. Aircraft have a 

lifespan of about 30 years, and many of the aircraft in the current fleet are 

expected to be in operation for many years to come. In addition, the 

financial pressures facing many airlines will make it difficult for them to 

upgrade their fleets with new, quieter aircraft. Failure to achieve FAA’s 

and NASA’s noise reduction goals could have implications for the 

implementation of NextGen, because continued noise problems at airports 

could constrain efforts to increase the safety and efficiency of the NAS—a 

key component of the NextGen strategy. 

We provided a draft of this report to the Department of Transportation and 

NASA for review and comment and neither had comments. 

FAA presently supports aviation noise R&D primarily in the areas of 

measuring and mitigating the impacts of aviation noise, while NASA 

focuses its efforts on technologies for reducing noise from aircraft engines 

and airframes, and the two agencies align their activities through 

partnerships and planning and coordinating mechanisms. 

FAA and NASA Use 

Partnerships and 

Planning and 

Coordinating 

Mechanisms to Align 

R&D on Noise 

Reduction 

 8

A similar provision is in the Senate bill for FAA reauthorization. As of the date of this 

publication, the House and Senate are discussing the reauthorization bills. 

Page 6 GAO-08-384 Aviation and the Environment 
FAA’s support of aviation noise R&D is part of its overall responsibility for 

reducing the impacts of aviation noise. In addition to R&D activities, FAA 

supports airports’ efforts to mitigate aviation noise mainly through its 

voluntary noise compatibility program, known as the Part 150 Noise 

Compatibility Program,9

 which provides guidance to airports on how to 

develop noise compatibility plans to mitigate noise on and around 

airports.10 FAA also administers grants through the Part 150 program that 

airports can use for noise mitigation efforts in areas exposed to significant 

aviation noise, defined as a 65 decibel day-night level (DNL 65 dB).11

FAA Supports Aviation 

Noise R&D Primarily 

through Partnerships with 

NASA, Academic 

Institutions, and the 

Aviation Industry 

Airports that participate in the Part 150 program can receive noise setaside funds from the Airport Improvement Program (AIP),12 which they 

must match to varying degrees, depending on their size.13 These funds can 

be used to, among other things, develop plans for noise mitigation, 

soundproof buildings, and support relocation by acquiring homes in areas 

with significant noise. According to FAA, it has provided about $5 billion 

in AIP grants, and airports have used about $2.8 billion in passenger 

 9

14 CFR 150. 

10As part of its environmental responsibilities, FAA also works through ICAO to foster 

international environmental standards, including those for noise, as well as recommended 

practices and guidance materials. 

11The impact of aviation noise is usually analyzed in terms of the extent to which the noise 

annoys people by interfering with their normal activities, such as sleep, relaxation, speech, 

television viewing, and school and business operations. The generally accepted model for

assessing the effects of long-term noise exposure is based on a correlation of the day-night 

average sound level, DNL, to the percentage of population highly annoyed by recurring

noise sound events. DNL is a noise descriptor or metric that takes into account the 

magnitude of the sound levels of all individual events that occur during a 24-hour period, 

the number of events, and an increased sensitivity to noise during typical sleeping hours 

(between 10:00 p.m. and 7:00 a.m.). The correlation shows that the percentage of people 

highly annoyed by noise exposure increases significantly above DNL 65 dB. Some aviation 

noise consultants have noted disadvantages of DNL as a metric to measure noise and 

suggest the use of supplemental metrics that measure the frequency and intensity of 

individual noise events that may provide a more adequate measure of aviation noise as

experienced by people. Some airports have included supplemental analysis such as the 

Number of events Above and the Time Above, within their noise studies. FAA requires the 

use of DNL for airport analysis but also allows for the use of supplemental metrics.

12The AIP program provides federal funds for development projects at the entire range of

the nation’s 3,400 airports—from small general aviation airports to the very largest airports

that handle several million passengers per year.

13According to FAA, noise projects are eligible for 80 percent funding under AIP for largeand medium-hub airports and 95 percent funding at small, nonhub, general aviation, and 

reliever airports. 

Page 7 GAO-08-384 Aviation and the Environment 
facilities charges (PFC)14 for Part 150 noise mitigation studies and projects.

In total, this funding amounts to nearly $8 billion for fiscal years 1982 

through 2007 (see table 1). 

Table 1: AIP and PFC Investments for Noise-Related Purposes for Fiscal Years 

1982-2007 

Dollars in millions 

AIP funds Funding 

Mitigation measures for residences $1,903 

Land acquisition 2,170 

Noise monitoring system 170 

Mitigation measures for public buildings 703 

Noise compatibility plan 87 

Total AIP funds $5,033 

PFC funds 

Multiphase $1,283 

Land acquisition 481 

Soundproofing 1,018 

Monitoring 31 

Planning 15 

Total PFC funds $2,828 

Grand total $7,861 

Source: FAA. 

FAA sponsors aviation noise R&D in a number of areas, including aviation 

noise measurement, the effects of aviation noise, the interrelationships 

between aviation noise and emissions, and flight procedures and 

technologies that can mitigate the impacts of noise on communities. FAA 

sponsors much of this research through partnerships with universities, 

other federal agencies, and industry. University research is generally part 

of FAA’s Air Transportation Centers of Excellence program. One of these 

Centers of Excellence, PARTNER, has conducted numerous noise-related 

R&D projects. See appendix I for a list of PARTNER participants and 

projects. PARTNER is a cooperative research organization that includes 10 

collaborating universities and approximately 50 advisory board members 

 14PFCs are fees that airports can charge passengers to fund FAA-approved projects. Not all 

airports charge these fees. 

Page 8 GAO-08-384 Aviation and the Environment 
who represent aerospace manufacturers, airlines, airports, state and local

governments, and professional and community groups. NASA, along with 

FAA and Transport Canada,15 is a sponsor of PARTNER. The collaborating 

universities and organizations represented on the advisory board provide 

equal matches for federal funds for research and other activities. 

PARTNER projects related to aviation noise involve identifying a means to

reduce aircraft landing noise, assessing the human health and welfare 

risks of aviation noise, developing online resources to better inform the 

public about aviation noise issues, and testing alternative aircraft descent 

patterns. For example, researchers are developing an integrated suite of 

three analytical tools—the Environmental Design Space, the Aviation 

Environmental Design Tool, and the Aviation Environmental Portfolio 

Management Tool—that can be used to identify interrelationships between 

noise and emissions. Data from these three tools will allow for assessing 

the costs and benefits of aviation environmental policy options. PARTNER 

has also designed and flight tested a nighttime Continuous Descent Arrival 

(CDA) procedure for the Louisville International Airport.16 This procedure 

is expected to allow aircraft to remain at cruise altitudes longer as they 

approach destination airports, use lower power levels, and thereby lower 

noise and emissions during landings. United Parcel Service plans to begin 

using the CDA procedure for its operations at Louisville International 

Airport in the near future. Other PARTNER projects include an effort to 

assess sonic booms from a new supersonic business aircraft and studies to 

better understand land use, development, and aviation noise around 

airports. 

FAA also supports research efforts at the Department of Transportation’s 

Volpe National Transportation Systems Center. The Volpe Center provides

research and support for the Integrated Noise Model, which airports use to 

model aviation noise at airports. Noise mitigation measures, such as 

residential soundproofing, are based on the noise contour maps generated 

by this model. The Volpe Center also conducts noise modeling studies. For 

example, it has conducted studies of aviation noise over the Grand Canyon 

in Arizona and over Bryce Canyon in Utah. FAA also has contracts with 

other entities such as Wyle Labs and Aerodyne Research to improve noise 

 15Transport Canada is the department within the government of Canada that is responsible 

for developing policies, regulations, and services for the Canadian transportation system. 

16John-Paul Clarke, et al., Partnership for Air Transportation and Emissions Reduction

Development, Design and Flight Test Evaluation of a Continuous Descent Approach

Procedure for Nighttime Operation at Louisville International Airport (Cambridge, MA: 

Jan. 9, 2006). 

Page 9 GAO-08-384 Aviation and the Environment 
measurement through modeling. For example, Wyle Labs performs work 

on the Model for Assessing Global Exposure to the Noise of Transport 

Aircraft, which estimates the global population exposed to noise and the 

effects of different mitigation scenarios. During the last decade, FAA has 

spent about $43 million to support aviation noise R&D (see table 2). 

Table 2: FAA Funds for R&D Efforts in Fiscal Years 1997-2007 

Fiscal 

Year Volpe Center PARTNER Other

1997 $770,000 $1,121,150

1998 841,000 1,654,000

1999 737,500 473,817

2000 1,040,000 577,000

2001 1,100,000 430,000

2002 889,000 869,000

2003 1,560,000 $1,775,000 1,002,000

2004 1,231,000 1,200,000 1,740,000

2005 1,962,750 1,651,250 3,134,527

2006 2,349,750 3,378,657 2,875,750

2007 2,432,750 3,361,500 2,819,859

Total $14,913,750 $11,366,407 $16,697,103

Source: FAA. 

NASA’s R&D Efforts Focus 

on Reducing Noise from 

Aircraft Engines and 

Airframes 

NASA’s efforts in the area of aviation noise are part of its overall 

aeronautical R&D program. NASA reorganized its aeronautical research 

plan in 2005 to focus on what it calls “fundamental research,” which takes

a technology to a point where it can be further matured by manufacturers 

and eventually integrated into new aircraft or engine designs. According to 

NASA, fundamental research includes (1) foundational research, which is 

the lowest level of the research pyramid on which advanced noise 

reduction technologies can be built; (2) discipline-level fundamental 

research, which includes the development of noise prediction methods 

that can be used to understand the noise reduction potential of various 

concepts; (3) multidiscipline-level fundamental research, which includes 

studying the trade-offs between noise, emissions, and performance that 

must be understood in order to determine the performance characteristics 

of a new aircraft; and (4) system-level fundamental research, which 

includes exploring research issues of interest to manufacturers when 

noise reduction technologies are integrated into a new aircraft and can 

include major wind-tunnel and flight tests. Figure 1 illustrates NASA’s 

Page 10 GAO-08-384 Aviation and the Environment 
research approach and shows that foundational research serves as the 

basis for the development of technologies and tools that can later be 

integrated into aviation subsystems and systems. 

Figure 1: NASA’s Research Approach Triangle 

MultiDisciplinary

Analysis and

Optimization

Development,

Validation and Application

Requirements and Needs

System Level

Subsystem Integration,

Test and Validation

Multi-Discipline

Technologies and Tool Development

Single-Discipline

Foundational Research

Basic Research

NA

SA In-house Research

NA

SA Research Announcement

 Funded Research

Industry and Other Government

Agency Cooperative Agreements

Knowledge and Capabilities

Sources: GAO and NASA.

NASA’s research on aviation noise focuses on noise emitted by aircraft 

and emphasizes the development of noise prediction methods, diagnostic 

methods for determining noise sources, and noise reduction methods that 

are applicable across a range of aircraft. NASA’s R&D plan is structured 

around reducing noise from three generations of aircraft, or vehicles, 

Page 11 GAO-08-384 Aviation and the Environment 
categorized as “N+1,” 17 to be implemented by 2015; “N+2,” to be 

implemented between 2020 and 2025;

 18 and “N+3,” to be implemented 

between 2030 and 2035. N+1 R&D focuses on one of the main sources of 

aviation noise—aircraft engines—by addressing fan noise as well as parts 

of the airframe that produce noise, such as landing gear and flap sides. For 

the N+2 generation of aircraft, NASA intends to develop tools and 

technologies that more closely integrate the airframe with the propulsion 

system through such means as the blended wing body concept. This 

concept, which calls for mounting the engines above the wings, would 

allow the airframe to shield and thereby reduce the effects of engine noise. 

The N+3 generation of aircraft, according to NASA, will have further 

dramatic reductions in noise and emissions and improvements in 

performance. A request for proposal for N+3 is expected in the spring of 

2008, with the objective of soliciting potential aircraft solutions and 

identifying key driving technologies for fundamental research investments. 

NASA states that noise reductions for N+2 and N+3 aircraft will depend 

strongly on the fundamental research that is carried out today. These 

NASA research efforts are also aimed at reducing emissions and fuel 

consumption, which in combination with noise reductions would help 

mitigate the environmental effects of future increases in air traffic. 

NASA is also working with others in the aeronautics research community 

on other advanced designs, such as the “silent aircraft” concept that was 

created by researchers from Cambridge University in Great Britain and the 

Massachusetts Institute of Technology. According to NASA, about $58 

million of the fiscal year 2007 subsonic fixed-wing research budget was 

directed toward noise-related research. 

In addition, NASA funds noise research conducted by outside 

organizations. According to NASA, it sponsors research by universities and

companies for its Fundamental Aeronautics Program through NASA 

Research Announcements (NRA). NASA officials note that the agency has 

made 215 NRA awards ranging from $100,000 a year to $1.5 million a year 

since December 2007, and that many of these awards were directed 

toward noise generation, propagation, and mitigation. 

 17“N” refers to the current generation of tube-and-wing aircraft entering into service in 2008 

such as the Boeing 787. 

18According to NASA estimates, the introduction of N+2 vehicles for Initial Operational 

Capability for military or cargo vehicles would be around 2020, and Entry Into Service for 

commercial vehicles would be around 2025.

Page 12 GAO-08-384 Aviation and the Environment 
FAA and NASA have taken advantage of a number of mechanisms to align 

their aviation noise R&D plans. According to officials from both agencies, 

their collaboration in PARTNER is one of the ways they align their 

aviation noise R&D activities. Both FAA and NASA are members of the 

advisory board for PARTNER, along with representatives from aerospace

manufacturers; airlines; airports; national, state, and local governments; 

professional associations; and community groups. The advisory board 

participates in strategic planning for PARTNER and semiannual reviews of 

the center’s research plan to ensure, among other things, that the plan 

addresses national and international issues, including those related to 

aviation noise. 

Participation in Advisory, 

Planning, and Coordinating 

Bodies Helps FAA and 

NASA Align and Monitor 

Their Aviation Noise R&D 

Plans 

FAA and NASA also seek to align their aviation noise research plans 

through participation in formal reviews of each other’s aviation noise 

research efforts. FAA representatives participate on NASA review panels 

to assess the technical quality, performance, and relevance of NASA 

research programs. In return, NASA participates in FAA’s REDAC, which 

is responsible for coordinating FAA’s research, engineering, and 

development activities with those of industry and other government 

agencies. REDAC was established in 1989 to advise the FAA Administrator 

on R&D needs in air traffic services; airport technology; aircraft safety; 

human factors; and environmental issues, including aviation noise. NASA’s 

Associate Administrator for Aeronautics Research is a member of REDAC, 

as are representatives from NASA’s research programs in aeronautics who 

serve on the committee’s subcommittees.19 FAA’s Director of the Office of 

Aviation Research is currently the Executive Director of REDAC. 

Another key component of FAA’s and NASA’s efforts to align their aviation 

noise R&D plans, according to officials from both agencies, is their 

participation in JPDO’s planning for NextGen. Both agencies are members 

of JPDO’s Environmental Working Group,20 which is headed by the FAA 

Director of the Office of Environment and Energy. NASA chairs the 

Environmental Working Group’s Technology Standing Committee, which 

focuses on the development of technologies to lessen NextGen’s 

environmental impacts. 

 19The four NASA aeronautics research programs are the Fundamental Aeronautics 

Program, the Airspace Systems Program, the Aviation Safety Program, and the Aeronautics

Test Program.

20JPDO has restructured its Integrated Product Teams into Working Groups. Nevertheless,

FAA and NASA continue to collaborate in the same roles and according to the Integrated

Work Plan. 

Page 13 GAO-08-384 Aviation and the Environment 
According to FAA and NASA officials, the mechanisms in place to align 

their agencies’ aviation noise R&D plans enable the two agencies and 

other stakeholders to periodically assess the potential for synergies or 

gaps in the agencies’ research activities. FAA’s and NASA’s aviation noise 

plans focus on different aspects of aviation noise. As we have previously 

noted, most of FAA’s R&D activities are presently concentrated on 

measuring and mitigating the impacts of aviation noise, whereas NASA’s 

R&D centers on developing technologies to reduce noise from aircraft 

engines and airframes. Both agencies’ participation in JPDO’s 

Environmental Working Group and in REDAC and FAA’s participation in 

NASA program reviews create opportunities for FAA and NASA to 

determine what adjustments in aviation noise R&D are needed to meet 

goals for reducing or mitigating the impacts of aviation noise. For 

example, the Environmental Working Group’s analysis determined that 

more near-term demonstration of noise reduction technologies on aircraft

was needed. According to FAA, the CLEEN proposal in the 

administration’s reauthorization bill, which will be discussed later in this 

report, addresses this gap. 

The extent to which FAA’s and NASA’s aviation noise R&D plans are 

aligned is indicated in JPDO’s strategic plans for NextGen, which serve as

a blueprint for improving the nation’s aviation system. These plans show 

how each agency’s R&D efforts will contribute toward meeting goals for 

reducing noise. Meeting these goals is critical for the success of NextGen 

because aviation noise is a major impediment to increasing the capacity of 

the NAS. JPDO’s goal is to reduce the impacts of significant aviation noise

(defined as DNL 65 dB) on communities despite the predicted growth in 

air traffic. Specifically, the Technology Standing Committee of the 

Environmental Working Group seeks to ensure the development of 

technologies to contribute to reducing the impact of aviation noise on 

communities. According to NASA, the technologies it is developing under 

its current aviation noise R&D program, if implemented in new 

generations of aircraft, would significantly contribute toward meeting this 

goal. 

The alignment of FAA’s and NASA’s aviation noise research plans is also 

reflected in the national aeronautics research plan issued by OSTP in 

Page 14 GAO-08-384 Aviation and the Environment 
December 2007.21 This plan, to which FAA and NASA contributed, outlines 

environmental goals that are aligned with JPDO’s. In line with the JPDO 

Environmental Working Group’s goal, the national plan states that the 

“environmental footprint of aviation must continue to shrink, even while 

accounting for an anticipated two to three times growth in capacity of the 

U.S. aviation system by 2025.” The national plan includes FAA and NASA 

goals for aviation noise research. For example, the plan’s near-term goals 

include researching and developing air traffic control procedures to 

reduce noise and developing improved tools and metrics to quantify and

characterize aviation’s environmental impacts. Long-term goals include 

developing new approaches and models for optimizing ground and air 

operational procedures. In addition, the technologies under development 

or planned for NASA’s N+1, N+2, and N+3 programs are included in the 

national plan. 

FAA and NASA have formalized their efforts to align their aviation noise 

R&D plans through memorandums of understanding (MOU) on R&D since 

October 9, 1998, with the latest dated May 2006.22 The most recent MOU 

describes how the agencies will coordinate their R&D efforts through the 

FAA/NASA Executive Research Steering Committee, which is co-chaired

by the agencies, with selected members from FAA and NASA offices 

involved with research programs. According to the MOU, this committee

ensures that complementary aviation and space transportation goals are 

defined for FAA and NASA and reflect each agency’s mission. The MOU 

further states that the two agencies will acknowledge and support their 

goals, coordinate their planning and resources to achieve the goals when 

appropriate, and monitor progress toward the goals and propose changes 

on the basis of changing requirements. 

 21OSTP’s charter is to advise the President on the effects of science and technology on 

domestic and international affairs and to lead interagency efforts to develop and implement

science and technology policies and budgets. OSTP’s plan, National Plan for Aeronautics

Research and Development and Related Infrastructure by the National Science and 

Technology Council (December 2007), establishes national research priorities, objectives, 

and schedules to achieve the identified objectives by 2020. 

22Memorandum of Understanding Between Department of Transportation, Federal 

Aviation Administration and National Aeronautics and Space Administration 

Concerning A Partnership to Achieve Goals in Aviation and Space Transportation (May 

15, 2006). 

Page 15 GAO-08-384 Aviation and the Environment 
FAA has established a goal for reducing the number of people exposed to 

significant noise from aircraft, while FAA and NASA have set goals for 

reducing noise from aircraft through technology development. However, 

questions about the sufficiency of federal funding for these efforts, the 

extent of government and industry participation in the later-stage 

development of noise reduction technologies, and airlines’ ability to 

incorporate the technologies in the near term make the achievement of 

FAA’s and NASA’s noise goals uncertain. Failing to achieve these goals 

could stall the implementation of NextGen, because continued noise 

problems at airports could constrain its expansion. 

FAA has established a target for reducing the number of people exposed 

to significant noise from aircraft, while FAA and NASA have set targets for 

noise reductions in aircraft to be achieved through technology 

development. FAA estimates that about 500,000 people in the United 

States are currently affected by significant aviation noise, defined as DNL 

65 dB or greater, and has set a goal of reducing this number by 4 percent

for each year through fiscal year 2012. The annual 4 percent reduction goal 

is an increase over FAA’s previous goal of an annual 1 percent reduction in

the population exposed to significant aviation noise. According to FAA, 

the 1 percent goal was exceeded in fiscal year 2006 when the percentage

of people exposed to significant noise decreased by 28 percent relative to

the 3-year average for calendar years 2000 through 2002. FAA stated that 

the main contributor to the decrease in population exposed to significant

noise is the early retirement of older, noisier aircraft primarily as the result 

of the air traffic downturn in the aftermath of the events of September 11, 

2001, and fuel inefficiency reasons. 

FAA and NASA Have 

Established Noise 

Reduction Technology 

Goals, but R&D 

Funding Issues and 

Other Factors Make 

the Achievement of 

Noise Reduction 

Goals Uncertain 

FAA and NASA Have Set 

Goals for Reducing 

Aviation Noise through 

New Technologies 

FAA has also set a goal that would more directly indicate the contribution 

of R&D to reducing aviation noise. FAA’s 2007 National Aviation Research

Plan qualitatively spells out R&D goals up to 2015. According to this plan,

FAA’s goal is to demonstrate that aviation noise can be significantly 

reduced to cost-effectively expand up to three times the current capacity 

of the air traffic system. FAA R&D activities from 2009 through 2013 to 

achieve these goals include (1) measuring current levels of aviation-related 

noise and emissions, (2) determining acceptable levels of noise and 

emissions, (3) developing models to predict the impact and benefits of 

changes, and (4) developing noise- and emission-reduction methods. 

Page 16 GAO-08-384 Aviation and the Environment 
Current activities are being conducted by PARTNER and the Volpe Center 

in collaboration with various industry stakeholders. 

NASA has established what it considers to be aggressive technology goals 

for its aviation noise R&D program that could be incorporated into 

aircraft. Under these goals, new technologies would be developed and 

incorporated in three succeeding generations of new aircraft, as we 

discussed in the preceding section of this report, thereby increasingly 

reducing what is known as EPN. NASA’s goals include a cumulative noise 

reduction of 32 EPN dB relative to the most current Chapter 4 noise 

standard23 for the next generation of aircraft, the N+1 generation,24 and this 

goal would be achieved by 2015. Next, noise from the N+2 generation of 

aircraft would be reduced to 42 EPN dB below the Chapter 4 standard, and 

this goal would be met between 2020 and 2025. Finally, noise from the N+3 

generation of aircraft would decline to 71 EPN dB below the Chapter 4 

standard during the period from about 2030 through 2035, thereby 

achieving NASA’s third noise reduction goal. Aviation noise would be 

reduced to the extent NASA predicts through the technologies it is 

researching if noise reduction were the only goal. However, when efforts 

are also made to achieve other goals, such as to reduce greenhouse gas 

emissions, noise reductions may be lower. FAA and the other members of 

JPDO’s Environmental Working Group have incorporated NASA’s aviation 

noise reduction goals in NextGen plans for reducing the environmental 

impacts of aviation. Table 3 identifies the time frames, goals, and research 

projects planned for NASA’s N+X generation aircraft program. 

 23In July, 2005, FAA issued a Federal Aviation Regulation (14 CFR 36.103 and 91.801-91.877) 

requiring that all new aircraft designs be subject to the current, more stringent ICAO noise

standards, know as Chapter 4 (known as Stage 4 standards in the regulation). Specifically, 

any new aircraft whose design was submitted to FAA for approval on or after January 1,

2006, must meet these standards adopted by ICAO in 2001. The less stringent Chapter 3

standard applies to most other aircraft. Under the Chapter 4 standards, none of an aircraft’s 

maximum noise levels at takeoff, landing, and approach can exceed Chapter 3 noise levels. 

Compliance with the standards is determined by subtracting an aircraft’s maximum noise 

levels at takeoff, flyover, and approach from the maximum permitted noise levels. The 

differences obtained are the noise limit margins. When the three margins are added 

together, the total must be 10 EPN dB or greater; and when any of the two margins are 

added together, the sum must be 2 EPN dB or greater. 

24The reductions would occur in aircraft that would replace such current aircraft as the

Boeing 737 and Airbus A320. Reductions would be different for larger aircraft and regional 

jets. 

Page 17 GAO-08-384 Aviation and the Environment 
Table 3: NASA’s N+X Generation Aircraft Program 

Program name N+1 generation N+2 generation N+3 generation

Time frame By 2015 Between 2020 and 

2025 

Between 2030 and 

2035 

Noise levela-32 EPN dB -42 EPN dB -71 EPN dB or greater 

Research

projects 

Engine noise 

reduction 

technologies 

Airframe noise 

source 

Investigation and 

mitigation study 

SAX-40 aircraft concept 

Aerodynamics and 

acoustic testing 

Predictive capabilities 

for subsonic aircraft 

Pulsed circulation 

control 

Plasma actuators for 

landing gear and highlift side edges 

NASA to solicit

proposals in spring 

2008 

Sources: GAO and NASA. 

a

Cumulative reduction below Chapter 4 standards. 

Meeting Noise Reduction 

Goals Is Uncertain 

Because of Questions 

about Federal R&D 

Funding, Government and 

Industry Participation, and 

Airline Investment 

Resources 

Despite efforts by FAA and NASA, to align aviation noise and other 

environmentally related R&D, concerns have arisen about whether the 

resources devoted to near-term R&D will be sufficient to achieve noise 

reduction goals for aircraft engines and airframes within the NextGen time 

frame. According to FAA, more funding is needed to mature noise 

reduction technologies beyond NASA’s research efforts. FAA is attempting 

to address this funding need through its proposed CLEEN consortium. 

Federal funding for aviation noise research has declined over the past 

decade, particularly for NASA, which provides most of the federal funding 

for aeronautics research, the category that includes aviation noise 

research. NASA’s budget for aeronautics research has dropped by about 

one-half over the past decade and is about $717 million for fiscal year 

2007. According to NASA, about $58 million of this funding goes toward 

noise-related research for subsonic fixed-wing aircraft. This downward 

trend contributed to NASA’s decision, previously discussed in this report, 

to refocus its aeronautical research plan on the earlier stages of the R&D 

process. 

According to FAA, most of the federal funding available for mitigating 

aviation noise is targeted to the Part 150 Noise Compatibility Program for 

soundproofing buildings around airports and acquiring or relocating 

properties that are exposed to high levels of aviation noise. In a 2002 

report on reducing the environmental impacts of aviation, the National 

Page 18 GAO-08-384 Aviation and the Environment 
Research Council’s Committee on Aeronautics Research and Technology 

for Environmental Compatibility25 noted that the vast majority of federal

expenditures on aviation noise is allocated to noise abatement at 

individual airports rather than to research on quieter aircraft and engines,

which could ultimately lead to reductions in aviation noise nationally and 

internationally. The report concluded that the funding for federal research 

programs was too low to remove noise as an impediment to the growth of 

aviation—a conclusion that FAA reiterated in a 2004 report to Congress on 

aviation and the environment.26

According to FAA, the administration is attempting to address the shortfall 

in aviation noise R&D spending in its proposal for reauthorizing FAA 

programs by seeking funding for programs to mature technologies that 

NASA and others originally developed. FAA officials stated that the 

proposed CLEEN Engine and Airframe Technology Partnership, for which 

the administration is seeking $111 million through fiscal year 2011, is 

intended to provide earlier maturation of aviation noise and emission 

reduction technologies while NASA focuses on longer-term fundamental 

research on noise and emissions. The CLEEN partnership, which is also in

the House reauthorization bill, would create a program for the 

development, maturation, and certification of engine and airframe 

technologies for aircraft over the next 10 years to reduce aviation noise 

and emissions. The proposals would require the FAA Administrator to 

establish an objective of developing aircraft technology that would be 

certified for incorporation into current aircraft models, resulting in a 

cumulative noise reduction of 32 EPN dB below ICAO’s Chapter 4 

standards, which is the same as the goal NASA has set for its N+1 aviation

noise R&D program. CLEEN would establish a research consortium of 

government, industry, and academic participants that would allow for the 

maturation of aviation noise technologies via demonstration projects for 

further refinement by the aviation industry and eventual incorporation into 

new aircraft designs. The proposal would also require the Administrator to 

set objectives for developing certifiable aircraft engine technologies for 

substantially reducing emissions. Because NASA’s current focus is on 

fundamental research to develop system-level technologies, the CLEEN 

proposal would not overlap with NASA’s R&D efforts. According to FAA, if

 25National Research Council, Committee on Aeronautics Research and Technology for 

Environmental Compatibility, National Academy of Sciences For Greener Skies: Reducing

Environmental Impacts of Aviation (Washington, D.C.: 2002). 

26FAA, Aviation and the Environment: A National Vision Statement, Framework for 

Goals and Recommended Actions (Washington, D.C.: December 2004). 

Page 19 GAO-08-384 Aviation and the Environment 
the proposed program is authorized and funded at the requested level,

FAA has reasonable confidence that noise goals will be achieved. 

NASA and FAA officials said they are making progress in meeting their 

noise reduction goals. NASA officials stated that NASA is progressing 

toward developing technologies that can be implemented in next 

generation aircraft engines and can meet the noise reduction goals set for

N+1. For example, NASA has established a partnership with Pratt & 

Whitney to demonstrate the benefits of a technology that would reduce 

noise. NASA and FAA have also worked with Boeing to demonstrate 

airframe and engine noise reduction technologies on a Boeing 777. FAA 

stated, and we have confirmed, that FAA has met its 2007 noise reduction

goals through September 2007. 

However, even with additional funding for aviation noise R&D, such as the 

amounts included in the CLEEN proposal, achieving FAA’s and NASA’s 

aviation noise goals for reducing noise from aircraft engines and airframes 

will remain a challenge because of uncertainties about the ability of 

aircraft engine and aircraft manufacturers to incorporate new noise 

reduction technologies into new engine and aircraft designs, and the need 

to consider trade-offs between noise reductions and reductions in 

emissions of greenhouse gases. NASA officials stressed that when NASA’s 

research ends, it will be up to engine and aircraft manufacturers to take 

the next steps to integrate the noise reduction technologies into engine 

and aircraft designs, and the manufacturers’ willingness to do so is not 

guaranteed. In addition, an expert we consulted noted that if

manufacturers do take the steps to integrate noise reduction technologies 

into new designs, the pace of noise reduction will also depend on the pace 

of development for new aircraft and aircraft engine designs. According to

FAA, the CLEEN proposal is to demonstrate to manufacturers that 

technologies initially developed by NASA and others are ready to be 

incorporated into new aircraft and engine designs. However, it is uncertain

whether the CLEEN proposal, if adopted, would be sufficient to achieve 

this objective. Concern about other environmental problems, such as 

global warming and air quality, may also limit the likelihood of achieving 

FAA’s and NASA’s noise reduction goals, since it may be technologically

challenging to design aircraft with reduced noise while, at the same time, 

achieving the significant reductions in greenhouse gases and other 

emissions that will be required. Although it is possible to design engines 

that produce less noise and fewer greenhouse gas emissions, the 

reductions in greenhouse gases could be limited in engines that produce 

substantially less noise. Furthermore, engines that burn less fuel are less 

costly to operate. As a result, air carriers may not be inclined to buy jets 

with engines that reduce noise but may be more expensive to operate. 

Page 20 GAO-08-384 Aviation and the Environment 
If R&D efforts lead to advancements in noise reduction technologies that 

can be incorporated in new aircraft in the near future, it is uncertain 

whether these advancements will contribute toward meeting FAA’s goals 

for reducing the number of people exposed to significant noise. As we 

noted in our recent testimony on aviation noise,27 implementing new noise 

reduction technologies, whether by integrating new, quieter aircraft into 

the fleet or by retrofitting aircraft, poses financial challenges for the 

aviation industry. Aircraft have an average lifespan of about 30 years, and 

airlines can take almost that entire period to pay for an aircraft. The 

current fleet is, on average, about half as many years old—11 years for 

wide-body aircraft and 14 years for narrow-body aircraft—and therefore, 

is expected to be in operation for many years to come. In addition, the 

financial pressures facing many airlines make it difficult for them to 

upgrade their fleets with new, state-of-the-art quieter aircraft, such as the 

Boeing 787 and Airbus A380. Currently, for example, U.S. carriers have 

placed a small proportion of the over 700 orders (40, or less than 6 

percent) that Boeing officials say the company has received for its 787 

model. Furthermore, no U.S. carriers have placed orders for the new 

Airbus A380, which is the world’s largest passenger aircraft. According to 

Airbus, the A380 produces significantly less noise than other large 

passenger aircraft currently in service. 

Failure to meet the aviation noise reduction goals outlined in FAA’s and 

NASA’s R&D plans could have significant implications for the 

implementation of NextGen. According to FAA, it generally takes 12 to 15

years to implement new technology on aircraft, and, therefore, NextGen 

technologies must be brought to maturity soon to meet the 2025 goal for 

implementing NextGen. According to FAA, without additional funding 

such as that proposed for CLEEN, near-term noise reduction goals may 

not be attained. However, if the technologies are developed that allow the 

goals to be met, FAA may also need to consider how to encourage airlines

to introduce quieter aircraft into their fleets as well as to retrofit existing 

aircraft with new equipment such as the satellite-based Automatic 

Dependent Surveillance-Broadcast (ADS-B) navigational system, which 

can allow aircraft to make more efficient, quieter approaches and 

descents. One way would be to offer operational advantages such as 

preferred takeoff and landing slots to quieter aircraft or aircraft equipped 

with ADS-B. Without significant noise reductions around the nation’s 

airports, efforts to expand their capacity could be stalled and the 

 27GAO-08-216T. 

Page 21 GAO-08-384 Aviation and the Environment 
implementation of NextGen delayed, thereby limiting FAA’s ability to 

efficiently manage the forecasted growth in air traffic. 

We provided copies of a draft of this report to the Department of 

Transportation and NASA for review and comment (see app. II). Both 

agencies had no comments. FAA and NASA did provide technical 

clarifications, which we incorporated into the report as appropriate. 

Agency Comments 

As agreed with your offices, unless you publicly announce the contents of

the report earlier, we plan no further distribution until 30 days from the 

date of this letter. At that time, we will send copies of the report to 

interested congressional committees, the Secretary of Transportation, the

Administrator of the FAA, and the Administrator of NASA. We will also 

make copies available to others upon request. In addition, the report will 

be made available at no charge on the GAO Web site at 

http://www.gao.gov. 

If you or your staffs have any questions about this report, please contact 

me at (202) 512-2834 or dillinghamg@gao.gov. Contact points for our 

Offices of Congressional Relations and Public Affairs may be found on the 

last page of this report. Individuals making key contributions to this report 

are listed in appendix III. 

Gerald L. Dillingham, Ph.D. 

Director, Physical Infrastructure Issues 

Page 22 GAO-08-384 Aviation and the Environment 
Appendix I: PARTNER Participants and

Projects 

Page 23 GAO-08-384 Aviation and the Environment 

Appendix I: PARTNER Participants and 

Projects 

Collaborating Universities 

Boise State University 

Georgia Institute of Technology 

Harvard University 

Massachusetts Institute of Technology 

Pennsylvania State University 

Purdue University 

Stanford University 

University of Missouri at Rolla 

University of North Carolina 

York University 

Advisory Board Members 

Aerodyne Research 

Aerospace Industries Association 

Airbus 

Air Line Pilots Association 

Air Transport Association of America 

Airports Council International – North America 

American Institute of Aeronautics and Astronautics 

Bay Area Air Quality Management District 

Bell Helicopter Textron 

Boeing 

Bombardier Aerospace 

Cessna Aircraft 

Commercial Aviation Alternative Fuels Initiative

CSSI 

Delta Airlines 

Environmental Compatible Air Transport System 

FAA Airports and Environmental Law Division 

FAA Air Traffic Environmental Programs Division 

FAA Airport Planning, Community and Environmental Needs Division 

FAA Centers of Excellence 

FAA Flight Standards 

FAA Office of Environment and Energy 

General Electric Aircraft Engines 

Gulfstream Aerospace 

Harris Miller Miller & Hanson 

Indiana Department of Transportation 

International Airline Passengers Association 

Larry Finegold & Son, Consultants 

Lockheed Martin Aeronautics 
Appendix I: PARTNER Participants and

Projects 

Logistics Management Institute 

Massachusetts Port Authority 

Metron Aviation 

Metropolitan Washington Airport Authority 

NASA Aeronautics Research Mission Directorate 

NASA Science Mission Directorate 

National Organization to Insure a Sound Controlled Environment 

O’Hare Noise Compatibility Commission 

Omega 

Palisades Citizens Association 

Pratt & Whitney 

Raisbeck Engineering 

Rannoch Corp. 

Regional Airport Authority of Louisville and Jefferson County 

Rolls Royce 

San Francisco International Airport/Community Roundtable 

Sikorsky Aircraft 

SNECMA 

Transport Canada 

United Parcel Service 

U.S. DOT Volpe National Transportation Systems Center 

U.S. EPA National Risk Management Research Laboratory 

Wyle Laboratories 

PARTNER Projects 

Airport Surface Movement Optimization

Alternative Fuels

Continuous Descent Arrival 

En Route Traffic Optimization to Reduce Environmental Impact 

Emissions Atmospheric Research 

Emissions Characteristics of Alternative Aviation Fuels

Energy Policy Act Study

Environmental Design Space

Health Effects of Aircraft Noise

Health Impacts of Aviation-Related Air Pollutants 

Investigation of Aviation Emissions Air Quality Impacts 

Land Use Management and Airport Controls (project completed) 

Lateral Alignment in Complex Systems (project completed) 

Low Frequency Noise Study (project completed) 

Measurement of Emissions

Network Restructuring Scenarios for ATO Forecasts

NoiseQuest

Page 24 GAO-08-384 Aviation and the Environment 
Appendix I: PARTNER Participants and

Projects 

Quantifying and Mitigating the Impact of Noise on People

Reduced Vertical Separation Minimums (project completed) 

Sonic Boom Mitigation

Valuation and Trade-offs of Policy Options

Page 25 GAO-08-384 Aviation and the Environment 
Appendix II: NASA Letter to GAO

Page 26 GAO-08-384 Aviation and the Environment 

Appendix II: NASA Letter to GAO 
Appendix III: GAO

A

 Contact and Staff 

cknowledgments 

Page 27 GAO-08-384 Aviation and the Environment 

Appendix III: GAO Contact and Staff 

Acknowledgments 

Gerald L. Dillingham, Ph.D., (202) 512-2834 or dillinghamg@gao.gov

In addition to the contact named above, Ed Laughlin (Assistant Director), 

Elizabeth Eisenstadt, Rosa Leung, and Maureen Luna-Long made key 

contributions to this report. 

GAO Contact 

Staff 

Acknowledgments 

(540163) 
GAO’s Mission The Government Accountability Office, the audit, evaluation, and 

investigative arm of Congress, exists to support Congress in meeting its 

constitutional responsibilities and to help improve the performance and 

accountability of the federal government for the American people. GAO 

examines the use of public funds; evaluates federal programs and policies; 

and provides analyses, recommendations, and other assistance to help

Congress make informed oversight, policy, and funding decisions. GAO’s 

commitment to good government is reflected in its core values of 

accountability, integrity, and reliability. 

The fastest and easiest way to obtain copies of GAO documents at no cost

is through GAO’s Web site (www.gao.gov). Each weekday, GAO posts 

newly released reports, testimony, and correspondence on its Web site. To

have GAO e-mail you a list of newly posted products every afternoon, go 

to www.gao.gov and select “E-mail Updates.” 

The first copy of each printed report is free. Additional copies are $2 each. 

A check or money order should be made out to the Superintendent of 

Documents. GAO also accepts VISA and Mastercard. Orders for 100 or 

more copies mailed to a single address are discounted 25 percent. Orders 

should be sent to: 

U.S. Government Accountability Office 

441 G Street NW, Room LM 

Washington, DC 20548 

To order by Phone: Voice: (202) 512-6000 

TDD: (202) 512-2537 

Fax: (202) 512-6061 

Contact: 

Web site: www.gao.gov/fraudnet/fraudnet.htm

E-mail: fraudnet@gao.gov

Automated answering system: (800) 424-5454 or (202) 512-7470 

Ralph Dawn, Managing Director, dawnr@gao.gov, (202) 512-4400 

U.S. Government Accountability Office, 441 G Street NW, Room 7125 

Washington, DC 20548 

Chuck Young, Managing Director, youngc1@gao.gov, (202) 512-4800 

U.S. Government Accountability Office, 441 G Street NW, Room 7149 

Washington, DC 20548 

Obtaining Copies of 

GAO Reports and 

Testimony

Order by Mail or Phone 

To Report Fraud,

Waste, and Abuse in 

Federal Programs 

Congressional 

Relations 

Public Affairs 

PRINTED ON RECYCLED PAPER