	Aviation’s Small but Growing Proportion of Total Emissions Contributes to Health and Environmental Effects

Aviation-related activities contribute to local air pollution and produce  greenhouse gases that cause climate change. Specifically, aviation emissions represent less  than 1 percent of air pollution nationwide, but their impact on air quality  could be higher in the vicinity of airports. Additionally, aviation’s greenhouse gas  emissions and potential contribution to climate change is expected to  increase. Nevertheless, according to EPA, there is growing public concern about the  health effects of the hazardous air pollutants and particulate matter  associated with aviation emissions. Key Federal Efforts to Address Aviation Emissions Include Near-Term Operational Changes and Longer-Term R&D Initiatives

Two key federal efforts, if implemented effectively, can help to reduce  aviation emissions—near-term NextGen initiatives and an array of R&D  programs over the longer term to fully enable NextGen and to reduce  aircraft emissions. In addition, the federal government, led by FAA and  NASA, has longer-term R&D programs in place to improve the scientific  understanding of the impact of aviation emissions in order to inform  decisions about emissions-reduction strategies, explore potential  emissions-reducing alternative fuels, and develop NextGen and aircraft  emissions-reduction technologies. ADS-B will allow for closer and safer  separations between aircraft and more direct routing, which will improve  fuel efficiency and reduce carbon dioxide emissions. Federal R&D Focuses on Long-Term Approaches to Addressing Aviation Emissions

We have previously reported that the federal government and industry  have achieved significant reductions in some aircraft emissions, such as  carbon dioxide, through past R&D efforts, and federal officials and  aviation experts agree that such efforts are the most effective means of  achieving further reductions in the longer term. According to FAA, this approach includes efforts to  improve the scientific understanding of the nature and impact of aviation  emissions and thereby inform the development of more fuel-efficient  aircraft, of alternative fuels that can reduce aircraft emissions, and of air  traffic management technologies that further improve the efficiency of  aviation operations. NASA, industry, and academia are important partners  in these efforts. Created in 2003, PARTNER carries on  what representatives of airlines, aircraft and engine manufacturers, and  experts in aviation environmental research have described as a robust  research portfolio. For example, the  Airspace Systems program supports research on air traffic management  technologies for NextGen, and the Fundamental Aeronautics program  focuses on removing environmental and performance barriers, such as  noise and emissions, that could constrain the capacity enhancements  needed to accommodate projected air traffic increases. Several Steps Can Be Taken to Help Reduce Aviation Emissions, but Challenges Remain to Be Addressed

Reducing aviation emissions includes steps that FAA and others can take  to move the implementation of NextGen forward and support R&D on  NextGen and emissions-reduction technologies, as well as technical,  financial, regulatory challenges facing the federal government, the aviation  industry, and Congress. As a partial response to the gap, the administration has proposed some  additional funding for FAA that could be used to further develop NASA’s  and others’ emissions- and noise reduction technologies. Fulfilling these requirements  will pose challenges to aviation because of the technical difficulties  involved in developing technologies that can simultaneously address air  pollutants, greenhouse gases, and noise; constraints on the airline  industry’s resources to invest in new aircraft and technologies needed to  reduce emissions and remain competitive; and the impact that emissions  regulations can have on the aviation system’s expansion and the financial  health of the aviation industry. Market-Based Initiatives to Reduce Aviation Emissions of Greenhouse Gases Could Pose Challenges for U.S. Airlines by Increasing Their Costs

Concerns about the environmental effects of greenhouse gas emissions  have grown steadily over the years, leading to national and international  efforts to limit them. Next Generation Air Transportation System: Progress and Challenges  Associated with the Transformation of the National Airspace System.
Why GAO Did This Study

Collaboration between the federal government and the aviation industry has led to reductions in aviation emissions, but growing air traffic has partially offset these reductions. The Federal Aviation Administration (FAA), together with the National Aeronautics and Space Administration (NASA), the Environmental Protection Agency (EPA), and others, is working to increase the efficiency, safety, and capacity of the national airspace system and at the same time reduce aviation emissions, in part, by transforming the current air traffic control system to the Next Generation Air Transportation System (NextGen). This effort involves new technologies and air traffic procedures that can reduce aviation emissions and incorporates research and development (R&D) on emissions-reduction technologies. Reducing aviation emissions is important both to minimize their adverse health and environmental effects and to alleviate public concerns about them that could constrain the expansion of airport infrastructure and aviation operations needed to meet demand. This testimony addresses (1) the scope and nature of aviation emissions, (2) the status of selected key federal efforts to reduce aviation emissions, and (3) next steps and challenges in reducing aviation emissions. The testimony updates prior GAO work with FAA data, literature reviews, and interviews with agency officials, industry and environmental stakeholders, and selected experts.

What GAO Found

Aviation contributes a modest but growing proportion of total U.S. emissions, and these emissions contribute to adverse health and environmental effects. Aircraft and airport operations, including those of service and passenger vehicles, emit ozone and other substances that contribute to local air pollution, as well as carbon dioxide and other greenhouse gases that contribute to climate change. EPA estimates that aviation emissions account for less than 1 percent of local air pollution nationwide and about 2.7 percent of U.S. greenhouse gas emissions, but these emissions are expected to grow as air traffic increases. Two key federal efforts, if implemented effectively, can help to reduce aviation emissions--NextGen initiatives in the near term and research and development over the longer term. For example, NextGen technologies and procedures, such as satellite-based navigation systems, should allow for more direct routing, which could improve fuel efficiency and reduce carbon dioxide emissions. Federal research and development efforts--led by FAA and NASA in collaboration with industry and academia--have achieved significant reductions in aircraft emissions through improved aircraft and engine technologies, and federal officials and aviation experts agree that such efforts are the most effective means of achieving further reductions in the longer term. Federal R&D on aviation emissions also focuses on improving the scientific understanding of aviation emissions and developing lower-emitting aviation fuels. Next steps in reducing aviation emissions include managing NextGen initiatives efficiently; deploying NextGen technologies and procedures as soon as practicable to realize their benefits, including lower emissions levels; and managing a decline in R&D funding, in part, by setting priorities for R&D on NextGen and emissions-reduction technologies. Challenges in reducing aviation emissions include designing aircraft that can simultaneously reduce noise and emissions of air pollutants and greenhouse gases; encouraging financially stressed airlines to purchase more fuel-efficient aircraft and emissions-reduction technologies; addressing the impact on airport expansion of more stringent EPA air quality standards and growing public concerns about the effects of aviation emissions; and responding to proposed domestic and international measures for reducing greenhouse gases that could affect the financial solvency and competitiveness of U.S. airlines.