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Report to the Chairman, Subcommittee on Aviation, Committee on 

Transportation and Infrastructure, House of Representatives:



United States General Accounting Office:



GAO:



February 2003:



Aviation and the Environment:



Strategic Framework Needed to Address Challenges Posed by Aircraft 

Emissions:



GAO-03-252:



GAO Highlights:



Highlights of GAO-03-252, a report to the Chairman, Subcommittee on 

Aviation, House Committee on Transportation and Infrastructure:



Why GAO Did This Study:



Although noise has long been a problem around airports, the

anticipated growth in demand for air travel has also raised questions

about the effect of airport operations on air quality. Aviationrelated

emissions of nitrogen oxides, which contribute to the

formation of ozone, have been of particular concern to many airport

operators. A federal study at 19 airports estimated that, by 2010,

aircraft emissions have the potential to significantly

contribute to air pollution in the areas around these airports.



GAO agreed to review efforts in the United States and other

countries to reduce emissions at airports and the effect of

improvements in aircraft and engine design on emissions.



What GAO Found:



Many airports have taken measures to reduce emissions, such as 

converting airport ground vehicles from diesel or gasoline to cleaner 

alternative fuels. While the actual impact of these measures is 

unknown, some measures (such as shifting to cleaner alternative fuels) 

have the potential to significantly reduce emissions, such as nitrogen 

oxides. In some casessuch as at Los Angeles and Dallas/Fort Worth 

airportsthe emission reduction measures have been imposed by federal 

or state agencies to bring severely polluted areas into attainment with 

the Clean Air Acts air quality standards or to offset expected 

increases in emissions from airport expansion projects. Many industry 

and government officials that GAO contacted said that new, stricter 

federal air quality standards that will go into effect in 2003, 
combined 

with a boost in emissions due to an expected increase in air travel, 

could cause airports to be subject to more federal emission control 

requirements. In 1998, a group of government and industry stakeholders 

was established to develop a voluntary nationwide program to reduce 

aviation-related emissions; however, thus far, the group has not agreed 

to specific objectives or elements of a program.



Other countries use many of the same measures as the United States to 

reduce emissions at airports. Two countries have imposed landing fees 

based on the amount of emissions produced by aircraft. However, U.S. 

officials question the effectiveness of these fees.



Research and development efforts by the federal government and the 

aircraft industry have improved fuel efficiency and reduced many 
emissions 

from aircraft, including hydrocarbons and carbon monoxide, but have 

increased emissions of nitrogen oxides, which are a precursor to ozone 

formation. As a result, many new aircraft are emitting more nitrogen 
oxides 

than the older aircraft they are replacing. For example, GAOs analysis 
of 

aircraft emission data shows that the engines employed on the newest 
models 

of a widely used jet aircraft, while meeting current standards for 
nitrogen 

oxide emissions, average over 40 percent more nitrogen oxides during 
landings 

and takeoffs than the engines used on the older models. Technologies 
are 

available to limit nitrogen oxide emissions from some other newer 
aircraft 

models. Many state and federal officials GAO contacted said that, in 
the long 

term, nitrogen oxide emissions from aircraft will need to be reduced as 
part 

of broader emission reduction efforts in order for some areas to meet 
federal 

ozone standards.



What GAO Recommends:



GAO recommends that the Federal Aviation Administration

(FAA) develop a strategic framework that addresses the

need for information on the extent and impact of emissions, identifies

reduction options, establishes goals and time frames for

achieving needed reductions, and defines the roles of government

and industry in developing and implementing reduction programs.



Contents:



Letter:



Results in Brief:



Background:



Airports and Airlines are Taking a Variety of Actions to Reduce 

Emissions, Although Specific Impact of These Actions Unknown:



Two Countries Have Introduced Emission-Based Fees:



Improvements in Aircraft and Engine Design Have Reduced Many Aircraft 

Emissions, but Nitrogen Oxide Emissions are Increasing:



Conclusion:



Recommendation for Executive Action:



Agency Comments:



Appendixes:



Appendix I: Objectives, Scope, and Methodology:



Appendix II: Types, Amounts, and Impact of Emissions from 

Aviation-related Sources:



Aviation-Related Emissions and Sources:



Health and Environmental Impact of Pollutants:



Appendix III: Federal, State, and International Responsibilities 

for Controlling Aviation-related Emissions:



Appendix IV: Efforts by Three States to Reduce Aviation-related 

Emissions:



California:



Texas:



Massachusetts:



Appendix V: Airports and Airlines Efforts To Reduce Emissions:



Aircraft:



Ground Support Equipment:



Providing Electric Power at Gates:



Passenger Vehicles:



Other Measures:



Appendix VI: Overview of Aircraft Fuel, Noise, and Nitrogen 

Oxide Reduction Technologies:



Appendix VII: Additional Information on Our Analysis of Aircraft 

Emissions:



Appendix VIIIComments from the National Aeronautics and 

Space Administration:



Appendix IX: GAO Contacts and Staff Acknowledgments:



GAO Contacts:



Staff Acknowledgments:



Tables:



Table 1: Aircraft Turbine Engine Emission Amounts during Cruising Per 

1000 Grams of Fuel Burned:



Table 2: Comparison of Emissions during Landing/Takeoff for Older and 

the Newest Model Boeing 737s:



Table 3: Comparison of Boeing 747 and 777 Emissions on a Per Aircraft 

Basis:



Table 4: Comparison of Boeing 747 and 777 Emissions on a Per Seat 

Basis:



Table 5: Comparison of Power, Engine Operating Pressures, and Nitrogen 

Oxides Emissions for Two Models of Boeing

737s:



Table 6: Health and Environmental Effects of Air Pollutants:



Table 7: Emission Information for Older Boeing 737s during Landing/

Takeoff:



Table 8: Emission Information for Newest Boeing 737s during Landing/

Takeoff:



Table 9: Additional Information on Comparison of Older and Newest Model 

Boeing 737 Landing/Takeoff Emissions:



Table 10: Additional Information on Comparison of Boeing 747 and 777 

Emissions on a Per Aircraft Basis:



Table 11: Comparison of Power, Engine Operating Pressures, and Nitrogen 

Oxides Emissions for a Boeing 737-300 and Its Most Common Replacement:



Figures:



Figure 1: Examples of Activities to Reduce Emissions:



Figure 2: NASAs Planned Funding for Nitrogen Oxide Research:



Figure 3: Major Components of a Turbofan Engine (Two-Shaft High Bypass 

Engine):



Abbreviations:



DOT: Department of Transportation:



EDMS: Emissions and Dispersion Modeling System:



EPA: Environmental Protection Agency:



FAA: Federal Aviation Administration:



GAO: General Accounting Office:



ICAO: International Civil Aviation Organization:



NASA: National Aeronautics and Space Administration:



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copyrighted materials separately from GAOs product.



United States General Accounting Office:



Washington, DC 20548:



February 28, 2003:



The Honorable John L. Mica

Chairman

Subcommittee on Aviation

Committee on Transportation and Infrastructure

House of Representatives:



Dear Mr. Chairman:



Although aviation-related activities result in the emission of 

pollutants that account for only about 0.5 percent of total air 

pollution in the United States, these pollutants are among the most 

prevalent and harmful in the atmosphere and are expected to grow. The 

Federal Aviation Administration (FAA) expects the demand for air travel 

in the United States to recover from the events of September 11, 2001, 

and then continue a long-term trend of 3.6 percent annual growth. This 

expected growth has heightened concerns among some communities, 

environmental groups, and others that airport operations will have an 

increasingly detrimental effect upon the environment. Although, to 

date, these groups have focused primarily on the noise generated by 

aircraft operations, they are becoming increasingly concerned about 

aviations impact on air quality. Our August 2000 report found that the 

operators of the nations 50 busiest airports considered that air 

quality issues would become a bigger concern and challenge for them in 

the future than any other environmental issue.[Footnote 1] Airport 

operators were particularly mindful of the effects on air quality of 

the increases in emissions due to airport growth. The emissions of most 

concern to many airport operators, as well as to many state and local 

air quality authorities, are nitrogen oxides, which are a primary 

contributor to the formation of ozone, a major pollutant in many 

metropolitan areas.



You asked us to provide information on how the aviation community is 

addressing current and future concerns about air quality. Specifically, 

you asked the following questions: (1) What efforts are being 

undertaken to reduce emissions from airport activities, and what are 

the outcomes of these efforts? (2) What additional efforts are being 

undertaken in other countries to reduce aviation-related emissions? and 

(3) How have improvements in aircraft and engine design affected 

aircraft emissions?



To address these questions, we reviewed the results of environmental 

reviews conducted over the past 3 years at major airports located in 

areas (called nonattainment areas) that have not attained air quality 

standards required by the Clean Air Act; surveyed air quality officials 

from the 13 states that have major airports in nonattainment areas; and 

visited seven airports. To identify trends in aircraft emissions, we 

analyzed aircraft landing and takeoff data for the U.S. commercial 

aircraft fleet in 2001 using a computer model developed by FAA. In 

addition, we interviewed and gathered information from officials 

representing FAA, the Environmental Protection Agency (EPA), the 

National Aeronautics and Space Administration (NASA), the International 

Civil Aviation Organization (ICAO), airlines, aircraft manufacturers, 

and state and local governments. We also reviewed previous reports on 

aviation emission issues and available information on international 

efforts to reduce aviation emissions. We conducted our work from 

September 2001 through February 2003 in accordance with generally 

accepted government auditing standards. See appendix I for additional 

information on our objectives, scope, and methodology.



Results in Brief:



Many of the nations busiest airports and airlines have taken actions 

to reduce the emissions from airport activities, such as converting 

shuttle buses to alternative fuels, decreasing the taxiing time of 

aircraft, and providing electricity to aircraft parked at gates, 

thereby allowing aircraft to turn off their more polluting power units 

while crews prepare the aircraft for the next flight. Although the 

actual impact of these measures is unknown, some measures have the 

potential to significantly reduce emissions from certain sources. For 

example, an initiative at Dallas/Fort Worth International and Houston 

airports to convert ground service equipment from diesel and gasoline 

to electric and alternative fuel engines is expected to cut nitrogen 

oxide emissions from such equipment by up to 75 percent. In some cases, 

federal or state agencies have imposed emission reduction measures on 

airports located in severely polluted areas (called nonattainment 

areas) to help bring these areas into attainment with the air quality 

standards of the Clean Air Act, or to offset expected increases in 

emissions from airport expansion projects. In other cases, airports or 

airlines have voluntarily undertaken the measures. For example, the 

ozone pollution in the Los Angeles metropolitan area has prompted the 

state to require emission reductions from all sources, including 

airports. State and local air quality agencies have negotiated with 

airlines that use five local airports, including Los Angeles 

International, to replace older, highly polluting ground support 

equipment--such as baggage handling and food service vehicles--with 

newer, less polluting equipment. State officials expect this action to 

reduce emissions from ground support equipment at the five airports by 

80 percent. In addition, our analysis of the environmental reviews 

conducted by FAA at major commercial airports located in nonattainment 

areas found that most proposed airport construction projects were not 

required to institute any emission reduction measures to comply with 

emission standards. However, FAA officials told us that in the future, 

approval of some projects in these areas may be less likely because of 

several factors, including increased focus on air quality by 

communities that oppose airport development. In addition, in 1998, a 

group of government and industry stakeholders was established to 

develop a voluntary nationwide program to reduce aviation-related 

emissions however, thus far the group has not defined specific 

objectives or established time frames for achieving emissions 

reductions. In 2003, EPA plans to begin implementing stricter ambient 

air quality standards for ozone and other pollutants, which could make 

it more difficult for some localities to achieve or maintain the 

standards. Many in the aviation industry as well as federal and state 

officials believe that the new standards, combined with the boost in 

emissions expected from increases in air travel, could cause airports 

to be subject to more federal emission control requirements in the 

future. Currently, 26 of the 50 busiest U.S. airports are located in 

areas that are not attaining the current 1-hour ozone standard; 

however, that number could increase to 38 under the stricter 8-hour 

ozone standard, according to EPA estimates.



Other countries use many of the same measures to reduce emissions at 

airports as the United States and, in addition, two countries have 

imposed landing fees based on the amount of emissions produced by 

aircraft. Switzerland and Sweden recently implemented emission-based 

landing fee systems as incentives for air carriers to reduce emissions 

from aircraft using airports in those countries. It is too soon to 

determine whether the fee systems have reduced emissions at these 

airports, although FAA officials question the effectiveness of such 

fees in reducing emissions. One U.S. airport, Boston Logan 

International, considered emission-based landing fees in 2001, but 

decided they would not be a practical option for reducing emissions--

particularly nitrogen oxides--because the fees would probably be too 

low to influence carriers use of lower-emitting aircraft.



Research and development by NASA and aircraft and engine manufacturers 

have led to engine and airframe improvements that have increased fuel 

efficiency and yielded environmental benefits, such as reduced carbon 

monoxide and other emissions. However, trade-offs among several 

factors, including engine performance, have also led to increases in 

emissions of nitrogen oxides, which are a precursor to ozone formation. 

As a result, some of the newest aircraft are emitting more nitrogen 

oxides than the older, noisier, and less fuel-efficient aircraft they 

are replacing. For example, our estimate of emissions produced by the 

U.S. commercial aircraft fleet in 2001 indicates that the engines used 

on the newest Boeing 737 models, which are widely used for domestic 

flights, average over 40 percent more nitrogen oxide emissions during 

landings and takeoffs than the engines primarily used on older-model 

Boeing 737s. Technologies are being introduced that limit nitrogen 

oxide emissions from some other newer aircraft models. Many state and 

federal officials we contacted stated that, in the long term, nitrogen 

oxide emissions from commercial aircraft will need to be reduced as 

part of broader emission reduction efforts in order for some areas to 

meet ozone standards. Both the environmental and aviation communities 

have also voiced concerns that emissions from aircraft, particularly 

nitrogen oxides, need to be further reduced. NASA, in association with 

the aviation community, is working on technologies to reduce emissions 

of nitrogen oxides, but it is unclear if such technologies can be 

introduced on commercial aircraft in the foreseeable future.



To address the growing impact of aviation on air quality and the lack 

of progress by the stakeholders group, we recommend that FAA develop a 

strategic framework that examines the extent and impact of nitrogen 

oxides and other aviation-related emissions; considers the 

interrelationship among emissions and between emissions and noise; 

includes goals, time frames, and options for achieving emission 

reductions; and specifies the roles of other government agencies and 

the aviation industry in developing and implementing emission reduction 

programs. FAA, EPA, and NASA generally agreed with our findings, and 

FAA agreed with our recommendation.



Background:



Although aviation-related activities currently account for only 0.5 

percent of total air pollution in the United States, the types of 

pollutants emitted by these activities are among the most prevalent and 

harmful in the atmosphere, and are expected to grow over time. The 

major sources of aviation-related emissions are aircraft, which emit 

pollutants at ground level as well as over a range of altitudes; the 

equipment (such as vehicles that transport baggage) that services them 

on the ground at airports; and vehicles transporting passengers to and 

from the airport. The amount of emissions attributable to each source 

varies by airport. A 1997 study of mobile source emissions at four 

airports found that ground access vehicles were the most significant 

source (accounting for 27 to 63 percent of total mobile source 

emissions), followed by aircraft (15 to 38 percent of the total) and 

ground service equipment (12 to 13 percent of the total).[Footnote 2] 

The emissions produced by these sources include carbon monoxide; sulfur 

dioxide; particulate matter; toxic substances (such as benzene and 

formaldehyde); and nitrogen oxides and volatile organic compounds, 

which contribute to the formation of ozone, a major pollutant in many 

metropolitan areas. In addition, aircraft emit carbon dioxide and other 

gases that have been found to contribute to climate change due to 

warming. According to the United Nations Intergovernmental Panel on 

Climate Change, global aircraft emissions accounted for approximately 

3.5 percent of the warming generated by human activities. (The types, 

amounts, and impact of emissions from aviation-related sources are 

described in detail in appendix II.):



Although only limited research has been done on the impact of projected 

growth in air travel on emissions, indications are that emissions are 

likely to continue increasing. FAA reported in June 2001 that the 

number of commercial flights is expected to increase about 23 percent 

by 2010 and about 60 percent by 2025.[Footnote 3] Each flight 

represents a takeoff and landing cycle during which most aircraft 

emissions enter the local atmosphere. In addition, an EPA study of 19 

airports projected that the proportion of mobile-source emissions of 

nitrogen oxides attributable to aircraft in the areas adjacent to these 

airports will triple from a range of 0.6 to 3.6 percent in 1990 to a 

range of 1.9 to 10.4 percent in 2010.[Footnote 4] Such projections, 

however, do not consider recent industry changes, such as airlines 

increased use of smaller aircraft and the financial uncertainties in 

the aviation industry. A recent report by the Department of 

Transportation indicated that the September 11, 2001, terrorist 

attacks, combined with a cut-back in business travel, had a major and 

perhaps long-lasting impact on air traffic demand.[Footnote 5]



A number of federal, state, and international agencies are involved in 

controlling aviation-related emissions. The Clean Air Act[Footnote 6] 

mandates standards for mobile sources of emissions such as aircraft, 

ground service equipment, and automobiles. As mandated by the act, EPA 

promulgates emission standards for aircraft, and has chosen to adopt 

international emission standards for aircraft set by ICAO, which was 

chartered by the United Nations to regulate international aviation and 

includes the United States and 188 other nations. As the United States 

representative to ICAO, FAA, in consultation with EPA, works with 

representatives from other member countries to formulate the standards. 

EPA and FAA work to ensure that the effective date of emissions 

standards permit the development and application of needed technology 

and give appropriate consideration to the cost of compliance, according 

to FAA officials. The officials also noted that EPA is responsible for 

consulting with FAA concerning aircraft safety and noise before 

promulgating emission standards. In addition to issuing aircraft 

emission standards, ICAO has studied aviation-related emission issues 

and issued guidance to its members on ways to reduce these emissions.



States can address airport emissions in plans, known as state 

implementation plans, [Footnote 7] that they are required to submit to 

EPA for reducing emissions in areas that fail to meet the National 

Ambient Air Quality Standards set by the EPA under the Clean Air Act 

for common air pollutants with health and environmental effects (known 

as criteria pollutants).[Footnote 8] Geographic areas that have levels 

of a criteria pollutant above those allowed by the standard are called 

nonattainment areas. Areas that did not meet the standard for a 

criteria pollutant in the past but have reached attainment and met 

certain procedural requirements are known as maintenance areas. The 

options available to states for controlling pollution from airports are 

limited because most emissions come from mobile sources, such as 

automobiles, which are already regulated by EPA, and states are 

generally preempted from issuing regulations on aircraft emissions 

because of EPAs federal responsibility in this area. FAA is 

responsible for enforcing the emission standards and for ensuring that 

emissions resulting from airport construction projects under their 

authority comply with the National Environmental Policy Act, which 

requires an environmental review of such projects, and the Clean Air 

Acts requirement that the projects comply with state implementation 

plans for attaining air quality standards. (See appendix III for 

additional information on federal, state, and international 

responsibilities concerning aviation-related emissions.):



Airports and Airlines are Taking a Variety of Actions to Reduce 

Emissions, Although Specific Impact of These Actions Unknown:



Many of the nations busiest airports and airlines that serve them have 

initiated voluntary emission reduction measures, such as converting 

shuttle buses and other vehicles from diesel or gasoline fuels to 

cleaner alternative fuels. While the actual impact of these measures is 

unknown, some measures (such as shifting to new cleaner gas or diesel 

engines or alternative fuels) have the potential to significantly 

reduce emissions, such as nitrogen oxides, volatile organic compounds, 

particulate matter, and carbon monoxide. The airports and airlines have 

undertaken these efforts for a variety of reasons, including 

requirements by states imposed as part of their plans to ensure that 

severely polluted areas (i.e., nonattainment areas) achieve the air 

quality standards established by the Clean Air Act and to gain federal 

approval for airport construction projects. In late 2003, EPA will 

begin implementing stricter standards for ozone, which could make it 

more difficult for areas to achieve or maintain attainment status. 

Representatives from the aviation industry as well as federal and state 

officials told us that the new air quality standards, combined with the 

boost in emissions expected from increases in air travel, could cause 

airports to be subject to more emission control requirements in the 

future. In addition, according to FAA officials, approval of some 

projects in these areas may be less likely because of several factors, 

including increased focus on air quality by communities that oppose 

airport development.



Airports and Airlines Voluntary Actions to Reduce Emissions:



Many of the nations busiest airports, in conjunction with the air 

carriers that serve them, have implemented voluntary control measures 

to reduce emissions from major sources, including aircraft, ground 

support equipment, and passenger vehicles entering and exiting the 

airport, according to our review of FAA documents and interviews with 

airport and state environmental officials. Specific guidelines or 

regulations for airports to reduce emissions from these sources do not 

exist, but some airports have been proactive in developing programs and 

practices that reduce emissions. Although the actual impact of these 

measures is unknown, some initiatives have the potential to 

significantly reduce emissions from certain sources. For example, a 

number of carriers at Dallas/Fort Worth International and Houston 

airports have agreed to voluntarily reduce emissions associated with 

ground service equipment by up to 75 percent. Figure 1 provides 

examples of activities to reduce emissions that have been implemented 

at U.S. airports. Appendix V provides more information on some 

airports voluntary efforts to reduce emissions.



Figure 1: Examples of Activities to Reduce Emissions:



[See PDF for image]



[End of figure]



Note: The information presented in this chart is not meant to include 

all activities for reducing emissions at airports. According to FAA, 

there are gaps in understanding how such activities effect various 

emissions, including various interrelationships among the emissions and 

their effects.



Most States Have Not Included Airports in Their Emission Control 

Strategies:



Only 3 of the 13 states with major commercial airports in nonattainment 

areas--California, Texas, and Massachusetts--have targeted airports 

for emission reductions. The remaining states have not included 

emission reductions at airports as part of their strategies for 

bringing nonattainment areas into compliance with the Clean Air Acts 

ambient air quality standards because they have attempted to achieve 

sufficient reductions from other pollution sources. Officials from 

these states noted that EPA has the authority to set emission standards 

for aircraft and nonroad vehicles, including ground support equipment 

at airports, which preempts the states regulation of these sources.



California and Texas face major ozone nonattainment problems--

California in the Los Angeles metropolitan area and Texas in the 

Dallas-Fort Worth and Houston metropolitan areas. According to air 

quality officials from both states, even after imposing all of the 

traditional emission control measures available, such as vehicle 

emission inspections, the three metropolitan areas still may not be 

able to reach attainment status for ozone by the 2010 deadline for Los 

Angeles and by the 2005 and 2007 deadlines for Dallas-Fort Worth and 

Houston, respectively. Despite potential legal challenges from 

airlines, both California and Texas turned to airports for additional 

emission control measures. Texas has negotiated an agreement with the 

Dallas/Fort Worth International and Houston airports and the airlines 

that serve them to reduce emissions attributable to ground support 

equipment by 90 percent. California has reached a similar agreement 

with the major airlines serving the five commercial airports in the Los 

Angeles nonattainment area to reduce emissions from ground support 

equipment.



Californias efforts to cut ground support equipment emissions in the 

Los Angeles area are part of a statewide campaign to reduce airport 

pollution. In addition to using its limited authority under the Clean 

Air Act to implement airport-related emission reductions, the state has 

also employed a certification process provided for in federal 

law.[Footnote 9] Under this provision, before FAA can approve a grant 

for any new airport, new runway, or major runway extension project, the 

governor must certify that the project complies with applicable air and 

water quality standards. California has developed criteria for 

determining whether a proposed airport expansion project would have an 

impact on the environment, including air quality. Unlike other states, 

California uses the criteria as a mandatory condition for project 

certification. If the project exceeds one of the criteria--by 

increasing the number of passengers, aircraft operations, or parking 

spaces and thereby producing an impact on the environment--the airport 

is required to implement emission mitigation measures in order to 

attain certification. Thus far, three airports--Sacramento 

International, San Jose International, and Ontario International--have 

initiated expansion projects that were required to comply with the 

certification standards. However, in a legal opinion issued in August 

2000, FAAs Office of Chief Counsel stated that California has no legal 

authority to impose operational limitations on airports through the 

certification process. According to FAA, California has not publicly 

responded to the opinion. A California air quality official told us 

that the state disagrees with the opinion and does not plan to change 

its certification process.



In 1999, Boston Logan International Airport began building a new runway 

to reduce serious flight delays. As a condition for approving the 

project, the state required the airport to cap emissions at 1999 levels 

(referred to as a benchmark) because it has determined that the 

airport is a significant contributor to Bostons serious ozone problem. 

To stay within the limit, the airport had considered reduction 

strategies that include charging higher landing fees during peak 

operating times to reduce congestion and the resulting emissions. Now 

that air traffic and emission levels have fallen off since the events 

of September 11, 2001, the operator of the Boston airport, the 

Massachusetts Port Authority, believes that peak pricing and other 

emission reduction strategies will not be needed for several years to 

keep emissions below 1999 levels. The Massachusetts Port Authority, 

however, continues to work with airport tenants to implement voluntary 

emission reduction strategies. More information on states efforts to 

reduce emissions appears in appendix IV.



Proposed Airport Projects Have Been Able to Conform to Current Air 

Quality Standards:



In addition to facing control measures as part of state strategies to 

attain the Clean Air Acts ambient air quality standards, airports must 

also submit most major construction project proposals for federal 

environmental review, which includes an evaluation of the proposed 

projects impacts on air quality. The National Environmental Policy Act 

and the Clean Air Act require that FAA perform environmental reviews of 

all airport projects that involve the federal government, such as the 

construction of federally subsidized runways. As part of this review 

process, FAA must determine that emissions from projects at airports in 

nonattainment and maintenance areas do not adversely interfere with 

states plans for the areas to reach attainment.



We examined all environmental reviews conducted by FAA at major 

commercial airports[Footnote 10] in nonattainment areas during the 3-

year period 1998 to 2001. These reviews include those required by the 

National Environmental Policy Act as well as those required under the 

Clean Air Act to ensure compliance with state implementation plans for 

achieving ambient air quality standards. During the period, FAA 

performed such reviews at 24 of the 26 major commercial airports in 

nonattainment areas. The projects reviewed included developing runways, 

expanding passenger terminals and air cargo and airline support 

facilities, and developing roadways and intersections on airport 

property.



Our analysis of airport environmental review documents showed that 

while air quality issues are a significant consideration for airports 

planning major development projects, emissions have not been a major 

obstacle in gaining approval for projects; however, FAA is concerned 

that increasing emissions from operations could jeopardize the approval 

of future expansion projects. In 12 of the 24 cases we examined, the 

environmental reviews stated that the airport expansion projects would 

not affect air quality in the regions. The environmental reviews for 7 

of these 12 projects estimated that emissions would decrease as a 

result of improvements in operational efficiency. For example, John F. 

Kennedy International Airport expected its proposed passenger terminal, 

air cargo, and airline support facilities expansion project to decrease 

the emission of nitrogen oxides by 207.2 tons per year by 2010 (about a 

5-percent reduction in total airport nitrogen oxide emissions[Footnote 

11]) because the project was expected to decrease the amount of time 

aircraft take to taxi from the runway to the terminal. For 8 of the 

projects, significant project-related emission increases resulted from 

construction activities and, although the increases were temporary, the 

airports were required, under EPAs general conformity rules, to adopt 

mitigation measures to allow FAA to determine that the projects 

complied with state implementation plans. In only 3 cases, was a 

significant permanent rise in emissions expected to result from the 

project. Five airports --Atlanta Hartsfield, Dallas/Fort Worth 

International, Los Angeles International, San Jose International, and 

Oakland International--were required to reduce emissions from other 

sources in order to mitigate the effects of the increased emissions 

expected from either project construction or operations related to a 

project. Atlanta Hartsfield, for example, committed to reduce emissions 

associated with construction by requiring construction equipment to be 

operated with catalytic converters that would reduce emissions and by 

using a massive conveyor system to haul fill material, thereby 

minimizing the use of trucks.



Although most recent airport construction projects in nonattainment 

areas met the requirements of the Clean Air Act, FAA officials noted 

that in the future, approval of some projects in these areas could be 

in jeopardy if state implementation plans did not make adequate 

allowances for emissions that could result from growth in aviation-

related activities or include provisions for airports to offset future 

increases. FAA noted that approval of projects is complicated by the 

fact that it is often difficult to determine if a development project 

complies with the state implementation plan because some plans do not 

contain an aviation emission component, while other plans use a model 

or methodology to calculate aviation emissions that is incompatible 

with FAAs model to determine a projects compliance with air quality 

requirements. In addition, FAA noted that approval of some projects may 

be complicated by an increased focus on air quality by community groups 

that oppose airport projects, the insistence of EPA and/or state and 

local air quality agencies on mitigation measures when FAA has 

determined that proposed projects will reduce emissions, and the 

general need to better understand aviation emissions. According to FAA, 

approval of airport construction projects may be further complicated by 

differences among federal and state air quality standards, especially 

when state standards are more restrictive, and differences among EPA 

and state/local air quality agencies on the appropriate analysis and 

mitigation measures. Also, FAA officials have noted an increasing trend 

for communities to demand under the National Environmental Policy Act 

that FAA undertake and disclose the effects of air toxics and health 

effects studies. Finally, although emissions from construction 

activities are temporary, if they are above allowable levels, FAA is 

required to undertake and issue a full determination that the project/

activity will conform to the state implementation plan.



Federal and State Programs for Reducing Airport Emissions:



FAA, EPA, and some states have developed programs to reduce emissions 

from aviation-related activities and established jointly with the 

aviation industry a process that has tried to reach a voluntary 

consensus on how to further reduce emissions. For example, as part of 

its Inherently Low-Emission Airport Vehicle Pilot Program, required by 

Congress in 2000,[Footnote 12] FAA awarded federal grants of up to $2 

million to each of 10 airports[Footnote 13] for alternative fuel 

vehicles and infrastructure. FAA is using the program to evaluate the 

vehicles reliability, performance, and cost-effectiveness in the 

airport environment. FAA initially anticipated that the program would 

reduce emissions by 22,584 tons of ozone, 314,840 tons of carbon 

monoxide, 384 tons of particulates, and 924 tons of sulfur dioxide 

during the projected lifetime of the airport equipment. To achieve this 

reduction, FAA expected the airports to purchase about 1,600 pieces of 

alternative fuel ground support equipment and 600 alternative fuel 

ground access vehicles, such as airport cars, buses, and shuttles. As 

of October 2002, FAA reported a slower-than-expected start-up of the 

program, with only five airports (Baltimore-Washington International, 

Dallas/Forth Worth International, Baton Rouge Metropolitan, Sacramento 

International, and Denver International) making notable progress on the 

program. According to FAA, the effects of the events of September 11, 

2001, have caused unforeseen delays and acquisition deferrals for many 

low-emission vehicle projects, particularly those that rely on airline 

financing to convert ground support equipment to alternative fuels.



Although FAA plans to provide $17.3 million for the Inherently Low-

Emission Airport Vehicle Pilot Program, airports and air carriers 

expressed the need for more federal funding to reduce emissions. Some 

airports have said that they would like flexibility in how the Airport 

Improvement Program[Footnote 14] or passenger facility charge[Footnote 

15] funds can be used to mitigate or offset emissions from expansion 

projects. For instance, Sacramento Airport officials stated that they 

would like the citys light rail system to be connected to the airport 

to reduce emissions from ground access vehicles. However, Airport 

Improvement Program or passenger facility charge funds cannot be used 

for emission mitigation projects located outside airport property. 

According to FAA, DOTs Congestion Mitigation and Air Quality grant 

program can be used to finance emission mitigation projects located 

outside of airport property.



Some states also have emission reduction assistance programs that are 

available to airports. The California Environmental Protection Agency 

developed the Carl Moyer Program, which is an incentive-based program 

that covers the incremental cost of purchasing airport vehicles with 

cleaner engines, including ground support equipment at airports. The 

program taps into available new environmental technologies to help the 

state advance clean air goals. It provides funds to private companies 

or public agencies to offset the incremental cost of purchasing the 

cleaner engines. The Texas Natural Resource Conservation Commission 

also established incentive funds for emission reduction efforts, 

similar to Californias program. As in California, the funds are not 

specifically designated for emission reductions at airports, but air 

carriers that are not participating in the agreement with the 

Commission to voluntarily reduce ground support equipment emissions can 

receive grants to convert their ground support equipment. Airlines that 

are part of the voluntary agreement would not be eligible for the 

incentive funds.



Some airport operators we spoke with would like EPA to set up a process 

in which airports could obtain credit for the amount of emissions 

reduced by their voluntary efforts; the credits can be banked by the 

airport to use at a future date to offset expected increases in 

emissions or they can be sold to other nonairport entities in the 

region that are required to offset emissions. The airport operators 

also indicated that having such a program encourages airport sponsors 

to undertake efforts to reduce emissions. Such an emission credit 

program is available in Washington State. Airports there can implement 

emission reduction efforts and obtain emission credits, which they can 

save and use to offset increased emissions from future expansion 

projects. Thus far, such a system has been adopted at one location, 

Seattle-Tacoma International Airport, which worked with the local clean 

air agency to establish a credit program for voluntary emission 

reduction actions. If airports are not allowed to save emission 

credits, any voluntary reductions will lower their emission baseline, 

which is used to calculate the impact of future emissions, and limit 

their options for any emission reductions required to obtain approval 

for future projects.[Footnote 16] Because of this situation, some 

airport officials told us that they have waited to initiate emission 

reduction efforts until the efforts are needed to gain approval for an 

expansion project. EPA encourages airports to contact their state and 

local air quality agencies and negotiate emission credit agreements, as 

was done by Seattle-Tacoma International Airport. However, according to 

FAA officials, this localized case-by-case approach to issuing emission 

credit is inefficient. Instead, FAA supports a consistent national 

approach that it believes would lessen the burden on airports to obtain 

emission credits from their respective states.



In 1998, FAA and EPA established a process--known as the stakeholders 

group--which includes representatives from state environmental 

agencies, airports, air carriers, and the aerospace industry to discuss 

voluntary efforts to lower nitrogen oxides and other emissions. They 

established the process because federal and industry officials told us 

that the current approach to reducing emissions--uncoordinated efforts 

by individual airports and states--was inefficient and possibly 

ineffective from a nationwide perspective. For example, some federal 

officials believe the current approach encourages airlines to move 

their more polluting equipment to airports that do not require cleaner 

vehicles, and the aviation industry is concerned about the impact that 

differing state requirements might have on their operations. According 

to EPA, another reason for establishing the process was concerns by 

EPA, state environmental agencies, and environmental groups about 

international emissions standards, particularly standards for nitrogen 

oxides.



The stakeholders group decided to focus on achieving lower aircraft 

emissions through a voluntary program because this strategy offered the 

potential for achieving desired goals with less effort and time than a 

regulatory approach. Initially, the groups discussions focused on 

emission reduction retrofit kits, which could be applied to some 

existing aircraft engines, but this was found to not be technically 

feasible. However, as the process evolved, the stakeholders expanded 

the focus to evaluating various emission reduction strategies for 

aircraft and ground support equipment. According to participants, the 

group is currently working to establish a national voluntary agreement 

for reducing ground service equipment emissions in the nearer term, 

similar to the agreement in California. In the longer term, the group 

is considering reductions in aircraft emissions through an approach 

known as environmental design space that recognizes the need to 

balance such reductions with other competing goals such as noise 

reduction, while assuring safety and reliability. FAA also noted that 

airport operators used the stakeholders group to highlight the need for 

more guidance on the process for ensuring that federal actions, such as 

the construction of new runways, conform to the appropriate state 

implementation plans. FAA and EPA issued guidance on the process in 

September 2002. The group had also commissioned a study to establish a 

baseline of aviation-related emissions and another study of options for 

reducing them. However, the study will not be completed because of 

resource constraints, according to participants.



FAA noted that the progress of the stakeholders group has been impeded 

by the impact of the events of September 11, 2001, on the airlines and 

the complex nature of addressing all stakeholders viewpoints to 

achieve consensus on a framework that can be applied nationally. The 

activities of the group were suspended after September 11, but resumed 

in May 2002. According to one member of the group, many participants 

have been frustrated by the groups slow progress, but they hope to 

define a nationwide program to reduce emissions from ground service 

equipment in 2003 and continue discussion of aircraft emission 

reduction options. However, the group has not defined specific 

objectives or established time frames for achieving its goal of 

reducing aviation-related emissions. Furthermore, the groups 

activities may be limited by the financial situation of participating 

air carriers.



New Air Quality Standards Will Pose a Challenge to Some States and 

Airports:



In late 2003, EPA plans to begin implementing a more stringent standard 

for ozone emissions, which could require more sources, including 

airports, to tighten controls on nitrogen oxides and some types of 

volatile organic compound emissions, which contribute to ozone 

formation. The new standard calls for concentrations of ozone not to 

exceed .08 parts per million over 8-hour blocks of time; the current 

standard requires concentrations not to exceed .12 parts per million 

over 1-hour blocks of time. Some state air quality officials that we 

spoke to believe that the continued growth of aviation-related ozone 

precursor emissions, coupled with such emissions from other sources, 

may affect their ability to meet to the new standard.



The implementation of the 8-hour standard for ozone could have 

significant implications for airports. Currently, 26 major commercial 

airports are located in nonattainment areas for ozone. EPA has yet to 

designate and classify which areas will not be in attainment with the 

8-hour standard. However, the agency estimates that under the 8-hour 

standard, areas containing 12 additional airports could be designated 

as nonattainment areas. Airports in these areas could be constrained in 

their ability to initiate development projects if they did not comply 

with the state implementation plans. EPA, however, believes that the 

new 8-hour standard provides an opportunity for the airports and the 

states that have not addressed airport emissions in their state 

implementation plans to identify airport emission growth rates when new 

plans are developed under the 8-hour standard.[Footnote 17]



Among the 13 state air quality officials we surveyed, 5 expect that 

aviation emissions will somewhat or moderately hinder their states 

ability to demonstrate compliance with EPAs new 8-hour ozone emission 

standard, and 3 stated that aviation emissions will greatly hinder 

their ability to comply.[Footnote 18] Some of these officials also said 

they are uncertain how their state will meet the new standards. Because 

the new 8-hour standard is more stringent, the states will need to 

develop more rigorous and innovative control measures for all sources 

and may have to rely on the federal government to reduce emissions from 

sources over which the state does not have jurisdiction, such as 

aircraft engines.



Two Countries Have Introduced Emission-Based Fees:



Other countries use many of the same measures to reduce emissions at 

airports as the United States and, in addition, two countries have 

imposed landing fees based on the amount of nitrogen oxide emissions 

produced by aircraft. Emission-based landing fees and other market-

based methods are currently being studied by ICAO and the former have 

been implemented in Switzerland and Sweden.[Footnote 19] Emission-based 

landing fees, although considered for Boston Logan International 

Airport, have not been implemented at any U.S. airports and many in the 

U.S. aviation community question their effectiveness.



ICAO established a working group to identify and evaluate the potential 

role of market-based options, including emission charges, fuel taxes, 

and emission-trading regimes,[Footnote 20] in reducing aviation-

related emissions. Thus far, the working group has concentrated on 

carbon dioxide emissions and has concluded that the aviation sectors 

participation in an emission-trading system would be a cost-effective 

measure to reduce carbon dioxide in the long term. The ICAO Assembly, 

the organizations highest body, has endorsed the development of an 

open emission-trading system for international aviation and has 

instructed its Committee on Aviation Environmental Protection to 

develop guidelines for open emission trading. The ICAO committee has 

also been studying emission charges or taxes as well as evaluating 

voluntary programs to reduce emissions. ICAOs current policy, adopted 

in 1996, recommends that emission-based fees be in the form of charges 

rather than taxes and that the funds collected should be applied to 

mitigating the impact of aircraft engine emissions.



Switzerland was the first country to implement a market-based system 

for reducing aviation-related nitrogen oxides and volatile organic 

compound emissions. In 1995, the Swiss federal government enacted 

legislation that allowed airports to impose emission charges on 

aircraft. In September 1997, the Zurich airport used this authority to 

establish emission-based landing fees as an incentive for air carriers 

to reduce emissions from aircraft using the airport. The use of 

emission-based landing fees has expanded to other airports in 

Switzerland and Sweden. The Geneva, Switzerland, airport implemented an 

emission-based landing fee similar to the fee scheme used in the Zurich 

airport in November 1998. Several Swedish airports also implemented 

emission fees after the Swedish Civil Aviation Administration approved 

such charges in January 1998. Similar to the system at Zurich airport, 

the Swedish airports reduced the landing charges so that income from 

emission charges is not considered an additional source of revenue.



The establishment of emission-based landing fees in Switzerland and 

Sweden has affected the operations of airlines with frequent flights to 

airports in these countries. According to a representative of a jet 

engine manufacturer, a Swiss airline purchased a number of new aircraft 

equipped with engines designed to emit lower amounts of nitrogen 

oxides. The representative said that the airline wanted the engines in 

order to reduce its landing fees at Swiss airports. However, the 

airline filed for bankruptcy in 2001 and has ceased operations. Only a 

few other airlines have expressed interest in equipping their new 

aircraft with engines that emit less nitrogen oxides because they are 

more expensive and less fuel-efficient and have higher operating costs. 

As of December 2002, no other airlines had purchased such engines.



No conclusive studies on the effectiveness of these emission-based 

landing fees have been completed. According to the Zurich Airport 

Authority, results of the emission-based landing fee can be shown only 

in the long term, making it difficult to quantify whether emissions 

such as nitrogen oxides or volatile organic compounds have been 

reduced. (FAA officials stated that the effects of emission-based fees 

can be estimated using existing models. For example, a 2001 ICAO 

working paper on market-based options for reducing carbon dioxide 

emissions found that enroute emissions charges would be insufficient to 

meet reduction targets.) Nevertheless, an aviation expert said that the 

emission-based landing fees have caused airlines to begin considering 

the cost of nitrogen oxides and volatile organic compound emissions as 

part of their business decisions.



Emission-based landing fees have not been introduced at any U.S. 

airports. Boston Logan International Airport considered implementing 

such fees to reduce emissions, but a 2001 study commissioned by the 

Massachusetts Port Authority, which operates the airport, determined 

them to be ineffective.[Footnote 21] The study found that emission-

based landing fees would be a small portion of commercial air carriers 

operating expenses and would be unlikely to affect their operational, 

purchasing, or leasing behavior substantially enough for them to 

consider using lower nitrogen-oxides-emitting aircraft and engines. 

Thus, the study concluded, the emission-based landing fees would not 

significantly induce commercial airlines to use aircraft engines 

emitting lower levels of nitrogen oxides.



Improvements in Aircraft and Engine Design Have Reduced Many Aircraft 

Emissions, but Nitrogen Oxide Emissions are Increasing:



Although research and development efforts by NASA and aircraft and 

engine manufacturers have led to engine and airframe improvements that 

have increased fuel efficiency and lowered carbon dioxide and 

hydrocarbon emissions, trade-offs among several factors, including 

engine performance, have also resulted in increased nitrogen oxide 

emissions. Our analysis of data on aircraft emissions during landings 

and takeoffs indicates that the newest generation of aircraft engines, 

while meeting international standards, can produce considerably more 

nitrogen oxide emissions than the older versions they are replacing. 

Engine options for some aircraft are now being introduced that reduce 

nitrogen oxide emissions. Additionally, NASA has ongoing research into 

technologies that could reduce nitrogen oxide emissions from jet 

engines to well below current standards. However, aviation industry 

representatives are unsure whether the technologies will ever be 

developed to the point where they can be incorporated into future 

production engines because of uncertainties about funding and other 

factors. Given the long lifespan of aircraft, even if the technologies 

are developed, it could be decades before enough airplanes are replaced 

to have a measurable effect on reducing nitrogen oxides. As a result, 

both the environmental and aviation communities have expressed concerns 

that emissions from aircraft, particularly nitrogen oxides, need to be 

further reduced.



Improvements in Aircraft and Engines Have Reduced Fuel Consumption and 

Most Emissions:



Improvements in jet engine design have led to increases in fuel 

efficiency and reductions in most emissions, particularly emissions 

from aircraft flying at cruise altitudes. Historically, the 

improvements in fuel consumption for new aircraft designs have averaged 

about 1 percent per year. The aviation industry and NASA, which are 

developing fuel reduction technologies, expect this rate to continue 

for the next two decades. Air carriers desire to control fuel costs 

provided the impetus for these efforts. (Appendix VI provides a brief 

overview of fuel reduction technologies.):



According to aircraft design experts, fuel consumption is the single 

biggest factor affecting the amount of most aircraft emissions. Table 1 

shows the amount of emissions produced by a typical aircraft turbine 

engine during cruising operations for each 1,000 grams of fuel burned.



Table 1: Aircraft Turbine Engine Emission Amounts during Cruising Per 

1000 Grams of Fuel Burned:



Type of emissions: Carbon dioxide; Amount of emissions (in grams): 

3,200.



Type of emissions: Water; Amount of emissions (in grams): 1,200.



Type of emissions: Nitrogen oxides (as nitrogen dioxide); Amount of 

emissions (in grams): 15.



Type of emissions: Carbon monoxide; Amount of emissions (in grams): 1.



Type of emissions: Sulfur oxides; Amount of emissions (in grams): 1.



Type of emissions: Hydrocarbons (as methane); Amount of emissions (in 

grams): 0.20.



Type of emissions: Soot (as carbon); Amount of emissions (in grams): 

0.02.



[End of table]



Source: National Research Council.



Note: For Greener Skies, Reducing Environmental Impacts of Aviation 

(Washington, D.C.: National Academy Press, 2002).



According to aviation experts, new aircraft designs are reducing carbon 

dioxide emissions by about 1 percent per year--the same rate at which 

fuel consumption is being reduced. ICAO expects this carbon dioxide and 

fuel reduction trend to continue for the next 20 years. Carbon monoxide 

and hydrocarbon cruise emissions are declining even faster than the 

fuel reduction rates. These emissions, which are formed when a portion 

of the fuel is only partially combusted, are much easier to minimize 

with the hotter engine temperatures of the new more fuel-efficient 

engine designs.



New Aircraft Designs Produce Significantly More Nitrogen Oxides during 

Landings and Takeoffs:



A byproduct of the improvements in jet engine design has been an 

increase in nitrogen oxide emissions during landings and takeoffs and 

while cruising, according to aviation industry experts. The new engine 

designs are capable of operating at higher temperatures and producing 

more power with greater fuel efficiency and lower carbon monoxide 

emissions. However, as engine-operating temperatures increase so do 

nitrogen oxide emissions. This phenomenon is most pronounced during 

landings and takeoffs, when engine power settings are at their highest. 

It is during the landing/takeoff cycle that nitrogen oxide emissions 

have the biggest impact on local air quality.



Our analysis of aircraft landing/takeoff emissions shows that newer 

aircraft produce considerably more nitrogen oxides than older models. 

We identified examples of aircraft models and engines introduced in the 

last 5 years and compared their emissions with emissions from older 

aircraft they might replace.[Footnote 22] We found, for example, that 

although the newer Boeing 737 series aircraft are more fuel-efficient, 

are capable of flying longer distances (or with more weight), emit less 

carbon monoxide and hydrocarbons, and produce less takeoff noise than 

their predecessors, they also produce 47 percent more nitrogen oxides 

during landing/takeoff (see table 2).[Footnote 23]



Table 2: Comparison of Emissions during Landing/Takeoff for Older and 

the Newest Model Boeing 737s:



Emission: Nitrogen oxides; Average emission (in pounds) per landing/

takeoff: Older Boeing 737: 12.1; Average emission (in pounds) per 

landing/takeoff: Newest Boeing 737: 17.8; Change: 47% increase.



Emission: Carbon monoxide; Average emission (in pounds) per landing/

takeoff: Older Boeing 737: 16.8; Average emission (in pounds) per 

landing/takeoff: Newest Boeing 737: 10.7; Change: 37% decrease.



Emission: Hydrocarbons; Average emission (in pounds) per landing/

takeoff: Older Boeing 737: 1.2; Average emission (in pounds) per 

landing/takeoff: Newest Boeing 737: 1.1; Change: 10% decrease.



[End of table]



Source: GAO.



Note: Landing and takeoff data for U.S. aircraft in 2001 obtained from 

AvSoft; emissions calculated using FAAs Emissions and Dispersion 

Modeling System, version 4.01. See appendix VII for additional 

information on our emission calculations and Boeing 737 models and 

engines.



Significantly higher emissions of nitrogen oxides during landing/

takeoff for the aircraft introduced in the last 5 years also occur in 

the largest aircraft. For example, the Boeing 777, the newest of the 

large jets, emits significantly more nitrogen oxides than comparable 

older aircraft. Table 3 compares a passenger model Boeing 747-400 with 

the Boeing 777 model and engines that it is most comparable to in 

seating capacity and range. Even before we adjusted for the greater 

seating capacity of the larger Boeing 747-400, we found that the most 

comparable Boeing 777--the 200ER model--produces 34 percent more 

nitrogen oxide emissions, even though ICAO data shows that the Boeing 

777 is quieter and more fuel-efficient than the older aircraft it is 

replacing. For example, on a per seat basis, the Boeing 777 can be as 

much as 30 percent more fuel-efficient than older model Boeing 747s.



Table 3: Comparison of Boeing 747 and 777 Emissions on a Per Aircraft 

Basis:



Emission: Nitrogen oxides; Emission (in pounds) per aircraft during 

landing/takeoff: Boeing 747-400: 103.5; Emission (in pounds) per 

aircraft during landing/takeoff: Boeing B777-200ER: 124.2; Change: 20 

percent increase.



Emission: Carbon monoxide; Emission (in pounds) per aircraft during 

landing/takeoff: Boeing 747-400: 47.7; Emission (in pounds) per 

aircraft during landing/takeoff: Boeing B777-200ER: 30.4; Change: 36 

percent decrease.



Emission: Hydrocarbons; Emission (in pounds) per aircraft during 

landing/takeoff: Boeing 747-400: 4.1; Emission (in pounds) per aircraft 

during landing/takeoff: Boeing B777-200ER: 2.4; Change: 41 percent 

decrease.



[End of table]



Source: GAO.



Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from 

AvSoft; emissions calculated using FAAs Emissions and Dispersion 

Modeling System, version 4.01. See appendix VII for additional 

information on our emission calculations and details about these 

aircraft and their contribution to the 2001 U.S. commercial fleet 

totals.



The Boeing B777-200ER data is the weighted average (based on 2001 

landings and takeoffs) for three different engines. The nitrogen oxides 

and other emission characteristics of these engines vary significantly.



As shown in table 4, the percentage increase in nitrogen oxides during 

landing/takeoff is 57 percent when the two aircraft are compared on a 

per seat basis (the amount of emissions divided by the number of seats 

on the aircraft).



Table 4: Comparison of Boeing 747 and 777 Emissions on a Per Seat 

Basis:



Emission: Nitrogen oxides; Emission (in pounds) per seat during 

landing/takeoff: Boeing 747-400: 0.287; Emission (in pounds) per seat 

during landing/takeoff: Boeing B777-200ER: 0.451; Change: 57 percent 

increase.



Emission: Carbon monoxide; Emission (in pounds) per seat during 

landing/takeoff: Boeing 747-400: 0.132; Emission (in pounds) per seat 

during landing/takeoff: Boeing B777-200ER: 0.110; Change: 16 percent 

decrease.



Emission: Hydrocarbons; Emission (in pounds) per seat during landing/

takeoff: Boeing 747-400: 0.011; Emission (in pounds) per seat during 

landing/takeoff: Boeing B777-200ER: 0.009; Change: 20 percent decrease.



[End of table]



Source: GAO.



Note: Landing and takeoff data for U.S. aircraft in 2001 obtained from 

AvSoft; emissions calculated using FAAs Emissions and Dispersion 

Modeling System, version 4.01. GAO analysis of AvSoft 2001 landing and 

takeoff data for U.S. aircraft. Emissions were calculated using FAAs 

Emissions and Dispersion Modeling System, version 4.01.



EPA and FAA regulate nitrogen oxide emissions and other emissions for 

U.S. commercial aircraft by requiring engine designs to meet ICAO 

standards for these emissions. Prior to production, all new engine 

designs are tested to determine the amount of nitrogen oxides and other 

emission characteristics.[Footnote 24] Only engines that meet the 

standards are certified for production. ICAO standards for nitrogen 

oxides were first adopted in 1981 and more stringent standards were 

adopted in 1993 (20 percent more stringent, effective 1996) and again 

in 1998 (16 percent more stringent, effective 2004). ICAO working 

groups are assessing whether or not the standards for nitrogen oxide 

emissions should be made more stringent than the standards that will 

take effect in 2004. Options being considered could make the standards 

between 5 percent and 30 percent more stringent between 2008 and 2012.



Under ICAO standards, newly designed engines and modified versions of 

older designs are allowed to produce significantly more nitrogen oxides 

than their predecessors. This is because the ICAO standards recognize 

that nitrogen oxides emissions are a function of engine power 

capability and operating pressure. Therefore, the standards allow for 

higher nitrogen oxide emissions for engines that (1) operate at higher-

pressure ratios, which increase their fuel efficiency and (2) produce 

more power. For example, the most common updated Boeing 737-700 

aircraft model and engine produces 41 percent more nitrogen oxides 

during landing/takeoff than the most common older version it is 

replacing (see table 5). Both engines will meet the new ICAO standard, 

which will go into effect in 2004 (the old engine betters the standard 

by about 15 percent, the new one by about 10 percent). A lower nitrogen 

oxide producing engine is available for the Boeing 737-700. This engine 

produces 18.5 percent more nitrogen oxides than the older Boeing 737-

700 that it is most comparable to in power and versatility.[Footnote 

25] However, this engine is less common in the fleet that then the more 

powerful one that offers more aircraft versatility. The database we use 

shows that in the U.S. fleet there were 8 Boeing 737-700s with the 

lower nitrogen oxides emitting engines and 118 with the more powerful 

engines.



Table 5: Comparison of Power, Engine Operating Pressures, and Nitrogen 

Oxides Emissions for Two Models of Boeing 737s:



Characteristic: Engine variant; Older model B737-300: CFM56 3B-1; 

Newest model B737-700: CFM56 7B-22.



Characteristic: Power (thrust) per engine; Older model B737-300: 89 

kiloNewtons; Newest model B737-700: 101 kiloNewtons.



Characteristic: Engine operating pressure ratio; Older model B737-

300: 22.4; Newest model:B737-700: 24.41.



Characteristic: Landing/takeoff nitrogen oxide emissions; Older 

model B737-300: 10.72 pounds; Newest model B737-700: 15.08 pounds.



[End of table]



Source: GAO.



Note: Landing and takeoff data for U.S. aircraft in 2001 obtained from 

AvSoft; emissions calculated using FAAs Emissions and Dispersion 

Modeling System, version 4.01. See appendix VII for additional 

information on our calculations and details about these aircraft.



There is an ongoing debate between the aviation and environmental 

communities over the best method for developing nitrogen oxide 

certification standards. Some in the aviation community want to 

maintain the current system under which the standards are made more 

stringent only when the engine manufacturers have produced engines that 

meet the new standards and new standards only apply to newly certified 

engines.[Footnote 26] (An industry official identified only two older 

types of engines that would not meet the more stringent 2004 nitrogen 

oxide standards.) Officials for the aviation industry said that it 

would be inadvisable to force more aggressive nitrogen oxide standards 

because new engine development programs are already complex and have 

many business and schedule risks. These officials added that the 

environmental regulatory process lacks cost-benefits data to defend a 

more aggressive approach that could result in extreme financial harm 

for engine and aircraft manufacturers if the approach delayed a new 

program. Further, some believe that if reductions in nitrogen oxides 

were to become a higher priority, it would be better to have market-

based incentives that reward lower nitrogen oxide emissions than have 

aggressive and rigid pass/fail regulatory barriers.



Moreover, some federal, state, and local environmental officials 

believe more incentives are needed to reduce aircraft nitrogen oxide 

emissions beyond the ICAO certification standards that are to take 

effect in 2004. They say that the current system gives little value to 

reducing nitrogen oxides in the many trade-offs among emissions, fuel-

consumption, and other factors made during engine design. They reason 

that if there were more incentives to reduce nitrogen oxide emissions 

beyond the certification requirements, these incentives would 

accelerate innovations that minimize degradations in other engine 

performance characteristics such as fuel efficiency.



While NASA and engine manufacturers have made continuous improvements 

for decades in technologies that have improved fuel efficiency, 

decreased noise, and decreased all emissions including nitrogen oxides, 

the design of the newest generation of engines has resulted in trade-

offs that favor fuel efficiency and increase nitrogen oxides. Two 

engine manufacturers have responded to this problem by developing 

options for several new engines that reduce nitrogen oxides. (General 

Electric has developed a dual annular combustor technology for one of 

its CFM56 engines and Pratt Whitney has developed a Technology for 

Affordable Low NOx [TALON] for some of its engines. This TALON 

technology is being used on some aircraft in the U.S. fleet.) According 

to NASA, about 100 engines using one of these technology options are 

currently in service on passenger and cargo aircraft. According to 

industry officials, knowledge gained from developing these options is 

contributing to ongoing nitrogen oxide reduction research.



Potential Success of Efforts to Reduce Aircraft Nitrogen Oxide 

Emissions Uncertain:



NASA, in association with jet engine manufacturers and the academic 

community, is working on several technologies to reduce nitrogen oxide 

emissions, although it is unclear if they can be introduced on 

commercial aircraft in the foreseeable future. If successfully 

developed and implemented, these technologies could significantly lower 

the emission of nitrogen oxides during landing and takeoff in new 

aircraft in stages over the next 30 years. However, the development of 

more fuel-efficient engines by NASA and the engine manufacturers, which 

are resulting in higher nitrogen oxide emissions,[Footnote 27] and the 

lack of economic incentives for airlines to support efforts to reduce 

nitrogen oxide emissions make the possibility of reaching these goals 

uncertain. In the last several years, increases in nitrogen oxide 

emissions from the more fuel-efficient engines have outpaced 

improvements made to reduce these emissions. Appendix VI provides more 

information on research to reduce nitrogen oxide emissions.



Adding to the uncertainty of introducing technologies to reduce 

nitrogen oxides is the limited federal funding for this research 

effort. NASA officials told us that in the past they developed their 

research to the full engine test level before engine manufacturers 

would take over responsibility for integrating the improvements into 

production-ready engines. However, budget cuts made in their emission 

research programs beginning in fiscal year 2000 have resulted in them 

ending their research at the engine component level below full engine 

testing. Figure 2 shows the funding for this program.



Figure 2: NASAs Planned Funding for Nitrogen Oxide Research:



[See PDF for image]



[End of figure]



Note: GAO analysis of information from NASA. Funding amounts are for 

the Ultra Efficient Engine Technology Program.



Industry officials and aviation experts agree on the importance of 

NASAs research and that NASA is focusing on the right mix of near-term 

and long-term technologies, but are critical of the amount of funding 

dedicated to nitrogen oxide reduction research. NASAs research to 

reduce nitrogen oxides is a component of its Ultra Efficient Engine 

Technology Program. The goal of this program is to develop technologies 

that will enable U.S. manufacturers to compete in the global 

marketplace for new commercial gas turbine engines. The current program 

is funded at $50 million per year. Industry representatives stated that 

shrinking budgets have made it difficult for NASA to maintain a level 

of effort at a critical mass for each project within the Ultra 

Efficient Engine Technology Program. Furthermore, they added that 

engine manufacturers could not afford to work with immature technology 

when they are engaged in new engine development projects. This is 

because new engine developments are tied into projects with the 

airlines, and the engines must meet tight cost, schedule, and 

performance goals if they are to win market share.



The Ultra Efficient Engine Technology Program is a scaled-back version 

of a larger aeronautical research program that was terminated in fiscal 

year 2000. NASA officials said that budget cuts have reduced research 

in the current program by about 40 percent from the previous program. 

In the previous program, research was typically developed to the point 

where the technology was integrated into the full engine system. In the 

current program, funding is only available to incorporate the 

technology into engine components. The National Research Council has 

concluded that the current funding level jeopardizes achieving program 

results and does not carry the research far enough for the engine 

manufacturing industry to readily adopt it. [Footnote 28]



As a result of the uncertainties surrounding emission reduction 

technology research, it is unclear when new production aircraft will, 

in the aggregate, start lowering landing/takeoff nitrogen oxide 

emissions on a per seat basis during the landing/takeoff cycle. Because 

of the 30-year projected life of new commercial aircraft, it could take 

decades before future new aircraft can contribute to nitrogen oxide 

reductions.



Concerns Over Emissions from Aircraft:



Both the environmental and aviation communities have voiced concerns 

about the need to better control the growth of aircraft emissions, 

particularly nitrogen oxides. Air quality officials from the 13 states 

that have airports in nonattainment areas told us that emission 

standards for aircraft should be made more stringent for a number of 

reasons. For example, several of those officials said that available 

control measures for other air pollution sources have been nearly 

exhausted. They noted that aircraft have not been as strictly regulated 

as other sources, such as automobiles, and that reductions from 

aircraft may be needed in the future for some areas to maintain 

attainment of the Clean Air Acts standards.[Footnote 29] Likewise, in 

2002, the National Academy of Sciences National Research Council 

reported that the advances that have led to increased efficiencies in 

individual airplanes are not sufficient to decrease the total emissions 

of the global fleet, which is increasing in response to accelerating 

demand.[Footnote 30] In the same vein, the Intergovernmental Panel on 

Climate Change reported in 1999 that although improvements in aircraft 

and engine technology and in the efficiency of the air traffic control 

system will bring environmental benefits, these will not fully offset 

the effects of the increased emissions resulting from the projected 

growth in aviation.:



Concerns about aircraft emissions have prompted calls for an improved 

approach for controlling them. For example, the National Research 

Council has recommended[Footnote 31] that the U.S. government carry out 

its responsibilities for mitigating the environmental effect of 

aircraft emissions and noise with a balanced approach that includes 

interagency cooperation in close collaboration with the private sector 

and university researchers. The Council emphasized that the success of 

this approach requires commitment and leadership at the highest level 

as well as a national strategy and plan that, among other things, 

coordinates research and technology goals, budgets, and expenditures 

with national environmental goals. Along the same lines, a recent 

industry article on the environmental effectiveness of ICAO emission 

standards suggested that a programmatic framework is required to guide 

the development of a consensus on policy options for further reducing 

aircraft emissions.[Footnote 32] Among the elements of the framework 

would be establishing the environmental need, the technical capability, 

the economic viability, and the regulatory consistency of each option.



Conclusion:



Aviations impact on local air quality is expected to grow as a result 

of projected increases in air travel. In addition, more attention will 

be focused on finding additional ways to reduce emissions from airports 

to enable localities to meet more stringent ozone standards, which go 

into effect in late 2003. In 1998, FAA, EPA, and industry officials 

established a stakeholders group to develop and implement a voluntary, 

nationwide program to reduce aviation-related nitrogen oxide emissions 

because they found the current approach--uncoordinated efforts by 

individual airports and states--inefficient for air carriers and 

potentially ineffective in reducing emissions nationwide. However, the 

stakeholders group has progressed slowly because of the complex nature 

of achieving consensus on all issues and, thus far, has not defined 

specific objectives or established time frames for achieving emissions 

reductions.



Despite its participation in the stakeholder group, FAA has not 

developed a long-term strategic framework to deal with these 

challenges. Moreover, FAA lacks a thorough study on the extent and 

impact of aviation emissions on local air quality. Without such 

management tools, FAA cannot assess the status or the effectiveness of 

its efforts to improve air quality. The study on aviation emissions 

prepared by the Intergovernmental Panel on Climate Change on aviations 

effect on the global atmosphere provides a model for a study that FAA 

could perform to develop baseline information and lay a foundation for 

a strategic framework. Such a study could accomplish the goals of the 

study that the stakeholders group commissioned, but never completed, as 

well as create an opportunity for making public the substance of its 

deliberations and for incorporating this substance in a plan for 

reducing emissions. Once completed, such a study would provide baseline 

information for setting goals and time frames to measure progress in 

reducing aviation-related emissions.



Recommendation for Executive Action:



We recommend that the Secretary, DOT, direct the Administrator of FAA, 

in consultation with the Administrator of EPA and Administrator of 

NASA, to develop a strategic framework for addressing emissions from 

aviation-related sources. In developing this framework, the 

Administrator should coordinate with the airline industry, aircraft and 

engine manufacturers, airports, and the states with airports in areas 

not in attainment of air quality standards. Among the issues that the 

framework should address are:



* the need for baseline information on the extent and impact of 

aviation-related emissions, particularly nitrogen oxide emissions;



* the interrelationship among emissions and between emissions and 

noise;



* options for reducing aviation-related emissions, including the 

feasibility, cost, and emission reducing potential of these options;



* goals and time frames for achieving any needed emission reductions;



* the roles of NASA, other government agencies, and the aviation 

industry in developing and implementing programs for achieving needed 

emission reductions; and:



* coordination of emission reduction proposals with members of ICAO.



Upon its completion, the Administrator, FAA, should communicate the 

plan to the appropriate congressional committees and report to them on 

its implementation on a regular basis.



Agency Comments:



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

the Environmental Protection Agency, and the National Aeronautics and 

Space Administration for review and comment. FAAs Director, Office of 

Environment and Energy, and senior managers in EPAs Office of Air and 

Radiation provided oral comments and NASAs Deputy Director provided 

written comments. (See appendix VIII.) The three agencies generally 

concurred with our findings and recommendation and provided technical 

corrections, which we incorporated as appropriate. In addition, FAA 

indicated that our report provides a helpful overview on the aviation 

emissions issue from the perspective of multiple stakeholders dealing 

with this important issue. FAA also indicated that it is providing 

heightened attention to aviation emissions through multiple efforts 

including improving data and modeling, working with the international 

community on improved standards, and considering alternative approaches 

to encourage reductions in aviation-related, ground-based and aircraft 

emissions.



As agreed with your office, unless you publicly announce the contents 

of this report earlier, we plan no further distribution until 5 days 

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

to interested congressional committees; the Secretary of 

Transportation; the Administrator, FAA; the Administrator, EPA; and the 

Administrator, NASA. We also will make copies available to others upon 

request. In:



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

at http://www.gao.gov. Please call me at (202) 512-3650 if you or your 

staff have any questions concerning this report. Major contributors to 

this report are listed in appendix IX.



Sincerely yours,



Signed by Gerald L. Dillingham:



Gerald L. Dillingham

Director, Physical Infrastructure Issues:



[End of section]



Appendix I: Objectives, Scope, and Methodology:



The Chairman of the Subcommittee on Aviation, House Committee on 

Transportation and Infrastructure asked us to provide information on 

the nature and scope of aviations impact on air quality and the 

opportunities that exist to reduce emissions from aviation activities. 

Specifically, our research focused on (1) what efforts are being 

undertaken to reduce emissions from airport activities and what the 

outcomes are of these efforts, (2) what additional efforts are being 

undertaken by other countries to reduce aviation-related emissions, and 

(3) how improvements in aircraft and engine design have affected 

aircraft emissions.



To address the three questions, we interviewed and collected material 

from federal officials at the Federal Aviation Administration (FAA), 

Environmental Protection Agency (EPA), and National Aeronautics and 

Space Administration (NASA). We also interviewed and collected 

information from representatives of aviation associations, airlines, 

and aircraft manufacturers. We also interviewed officials from 

airports, state and local governments, and nongovernmental 

organizations. In addition, we reviewed our previous studies and those 

of EPA, the Natural Resources Defense Council, the International Panel 

on Climate Control, and other aviation-related environmental studies.



To address the first research question, we identified the nations 50 

busiest commercial service airports and determined that 43 of these 

airports are located in areas designated as nonattainment or 

maintenance with respect to requirements of the Clean Air Act. We 

reviewed and summarized environmental review documents submitted from 

1997 through 2001 for the 43 airports to identify the nature of 

emissions from aviation activities and efforts to mitigate them. We 

also reviewed applicable sections of state implementation plans for the 

13 states in which the 43 airports are located to identify emission-

related sources and determine the nature of mitigation measures being 

undertaken. We also conducted comprehensive computer literature 

searches to identify the environmental effects of airport operations.



To also address the first research question and to provide information 

on the roles and responsibilities of states in relation to aviation-

related emissions, we identified 13 states with airports located in air 

quality problem areas and conducted a telephone survey with state air 

quality authorities in these areas to obtain information on oversight/

regulatory responsibilities for airport activities. We selected the 

states by first identifying the top 50 busiest commercial service 

airports on the basis of the number of air carrier landings and 

takeoffs in fiscal year 2001. In those states, 26 airports were 

identified as being located in areas designated as nonattainment for 

ozone. The 26 airports are located in the following 13 states: Arizona, 

California, Georgia, Kentucky, Maryland, Massachusetts, Missouri, New 

Jersey, New York, Pennsylvania, Texas, Illinois, and Virginia. We 

reviewed applicable sections of the Clean Air Act, the National 

Environmental Policy Act, states air quality laws, and International 

Civil Aviation Organization (ICAO) policies that defined air emissions 

standards applicable to aviation-related activities and agencies role 

and responsibilities for administering them.



For the first research question, we also selected seven airports for 

case studies--Los Angeles International, Boston Logan International, 

Sacramento International, Dallas/Fort Worth International, Chicago 

OHare International, George Bush International/Houston, and Atlanta 

Hartsfield airports. We selected these airports on the basis of 

passenger traffic, air quality status, and initiatives undertaken to 

deal with airport-related emissions. At each location, we interviewed 

and gathered data from officials representing FAA and EPA regional 

offices, airports, state and local governments, and nongovernmental 

organizations on efforts to reduce emissions.



To address the second research question, we identified international 

efforts to reduce aviation-related emissions through our interviews 

with FAA, Department of State, ICAO, airport, airline, and 

nongovernmental agency officials. We conducted comprehensive computer 

literature searches to identify other international airports and to 

gather information on the efforts being undertaken by these airports to 

reduce aviation-related emissions. Our searches identified aviation 

reduction programs at European airports, including Switzerland and 

Sweden. We reviewed materials from Swiss and Swedish federal civil 

aviation officials on these efforts. We also reviewed proposed European 

Unions policies on reducing aviation-related emissions.



Finally, to address the third research question, we interviewed jet 

engine manufacturers, NASA researchers, and a university researcher to 

obtain information on efforts to reduce aircraft emissions. In 

addition, we calculated the landing and takeoff emissions for every 

aircraft model and engine combination in the U.S. 2001 commercial fleet 

for which data were available. Next, we looked for emission trends by 

identifying instances in which new model/engine combinations had been 

introduced in the last 5 years. We then compared the landing/takeoff 

emission characteristics of these newer aircraft with the emissions of 

the older aircraft they were most likely to replace. We identified 

examples of emissions trends for new aircraft. We did not perform a 

complete analysis of all trends.



In performing this analysis, we obtained the following information on 

every aircraft in the U.S. commercial aircraft fleet:



* specific model and engine,



* year 2001 landing/takeoff counts,



* aircraft age, and:



* seating capacity.



This information came from AvSoft, a company that specializes in 

detailed data on commercial aircraft. We summarized this information 

for each specific model and engine combination. We then calculated the 

landing/takeoff emissions for each of these combinations using the 

Emissions and Dispersion Modeling System (EDMS), version 4.01 software 

developed by FAA for this purpose.



EDMS software calculates landing/takeoff emissions for four major 

criteria pollutants: carbon monoxide, volatile organic compounds, 

nitrogen oxides, and sulfur dioxides. The calculations take into 

account characteristics of specific aircraft model/engine combinations 

as well as airport-specific variations in the landing/takeoff cycle. We 

calculated the emissions for a representative generic airport using 

EDMS default values. Key values used in our EDMS calculations were:



* emission ceiling height: below 3,000 feet;



* taxi-time: 15 minutes;[Footnote 33] and:



* takeoff weight: EDMS default value.



To determine the reliability of the software and data we used, we 

reviewed FAAs and AvSofts quality controls, customer feedback 

information, and self-assessments. A weakness AvSoft identified with 

the data we used was a tendency to undercount the landings/takeoffs for 

smaller aircraft (aircraft with 70 seats or less). In addition, the 

EDMS software does not have complete information on some aircraft 

models and engines (particularly the less common ones). In addition, 

the EDMS software does not have complete information on some of the 

less common aircraft models and engines. This weakness, however, did 

not affect the trends we identified because of the limited use of these 

models and engines. On the basis of our experience working with the 

data and the software, we determined that the vendors were providing 

reliable products for the purposes for which we used them and that 

additional data and software reliability assessments were not needed to 

support our conclusions.



During the review, the following aviation experts reviewed our methods 

and report drafts for accuracy and balance: John Paul Clarke of the 

Massachusetts Institute of Technology; Mary Vigilante of Synergy 

Consulting, Inc.; and Ian Waitz of the Massachusetts Institute of 

Technology.



[End of section]



Appendix II: Types, Amounts, and Impact of Emissions from Aviation-

related Sources:



Most emissions associated with aviation come from burning fossil fuels 

that power aircraft, the equipment that services them, and the vehicles 

that transport passengers to and from airports. The primary types of 

pollutants emitted by aircraft and airport-related sources are volatile 

organic compounds, carbon monoxide, nitrogen oxides, particulate 

matter, sulfur dioxide, toxic substances such as benzene and 

formaldehyde, and carbon dioxide, which in the upper atmosphere is a 

greenhouse gas that can contribute to climate change. When combined 

with some types of volatile organic compounds in the atmosphere, carbon 

dioxide forms ozone, which is the most significant air pollutant in 

many urban areas as well as a greenhouse gas in the upper atmosphere. 

Particulate matter emissions result from the incomplete combustion of 

fuel. High-power aircraft operations, such as takeoffs and climb outs, 

produce the highest rate of particulate matter emission due to the high 

fuel consumption under those conditions. Sulfur dioxide is emitted when 

sulfur in the fuel combines with oxygen during the combustion process. 

Fuels with higher sulfur contents produce higher amounts of sulfur 

dioxide than low-sulfur fuels. Ozone and other air pollutants can cause 

a variety of adverse health and environmental effects.



Aviation-Related Emissions and Sources:



Aircraft emit pollutants both at ground level as well as over a range 

of altitudes. At most U.S. airports, aircraft can be a major source of 

air pollutants. The major air pollutants from aircraft engines are 

nitrogen oxides, carbon monoxide, sulfur dioxide, particulate matter, 

and volatile organic compounds. The burning of aviation fuel also 

produces carbon dioxide, which is not considered a pollutant in the 

lower atmosphere but is a primary greenhouse gas responsible for 

climate change. During the landing and takeoff cycles, and at cruising 

altitudes, aircraft produce different levels of air pollutant 

emissions. Emission rates for volatile organic compounds and carbon 

monoxide are highest when aircraft engines are operating at low power, 

such as when idling or taxiing. Conversely, nitrogen oxide emissions 

rise with an increasing power level and combustion temperature. Thus, 

the highest nitrogen oxide emissions occur during aircraft takeoff and 

climb out. In addition, aircraft have mounted auxiliary power units 

that are sometimes used to provide electricity and air conditioning 

while aircraft are parked at terminal gates and these units emit low 

levels of the same pollutants as aircraft engines. When flying at 

cruising altitudes, aircraft emissions, including carbon dioxide, 

nitrogen oxides, and aerosols that are involved in forming contrails 

and cirrus clouds, contribute to climate change.



Ground support equipment--which provide aircraft with such services as 

aircraft towing, baggage handling, maintenance/repair, refueling, and 

food service--is also a source of emissions at airports. This equipment 

is usually owned and operated by airlines, airports, or their 

contractors. According to EPA, the average age of ground support 

equipment is about 10 years, although some of the equipment can last 

more than 30 years with periodic engine replacement. Most ground 

support equipment is powered by either diesel or gasoline engines, and 

older engines pollute more than newer engines. Emissions from ground 

support equipment include volatile organic compounds, carbon monoxide, 

nitrogen oxides, and particulate matter. At some airports, airlines and 

the airport operators are introducing electric and alternative-fuel 

powered ground support equipment.



Emissions from passenger vehicles and trucks, referred to as ground 

access vehicles, are an important consideration at airports. Heavy 

traffic and congestion in and around airports result from the influx of 

personal vehicles, taxis and shuttles discharging and picking up 

passengers, and trucks hauling airfreight and airport supplies. Such 

traffic generates significant amounts of the emissions including carbon 

monoxide, volatile organic compounds, and nitrogen oxides. Several 

states that we surveyed indicated that automobiles are the major source 

of volatile organic compounds, carbon monoxide, particulate matter, and 

nitrogen oxides in areas with air quality problems at airports. This 

situation has occurred despite the fact that automobile emissions have 

been reduced on a per vehicle basis by 98 percent in the past 25 years.



Other sources of emissions at airports include construction activities, 

electric power generating plants, and maintenance operations. The air 

pollutants emitted by these activities can include particulate matter, 

nitrogen oxides, carbon monoxide, and sulfur dioxide.



The information available on the relative contribution of aviation-

related activities to total emissions in an area is limited, but it 

indicates that these activities account for a small amount of air 

pollution and the proportion attributed to airports is likely to grow 

over time. According to EPA, aircraft, which are the only source of 

emissions unique to airports, currently account for about 0.6 percent 

of nitrogen oxides, 0.5 percent of carbon monoxide, and 0.4 percent of 

the volatile organic compounds emitted in the United States from mobile 

sources.[Footnote 34] In cities with major airports, aircraft-related 

emissions could be higher or lower. In a 1999 study of 19 airports 

located in 10 cities,[Footnote 35] EPA found that the proportion of 

nitrogen oxide emissions from mobile sources attributed to aircraft 

ranged from 0.6 percent to 3.6 percent in 1990. EPA also found that 

aircraft accounted for 0.2 percent to 2.8 percent of volatile organic 

compound emissions from mobile sources in the 10 cities during the 

period. From information contained in a recent study of emissions at 

Dallas/Fort Worth International Airport we estimated that aircraft 

produced about 3 percent of the nitrogen oxides and about 5 percent of 

the carbon monoxide present in the metropolitan area.[Footnote 36] A 

1999 study of emissions at Chicago OHare International Airport found 

that aircraft and the airport as a whole emitted about 1.6 percent and 

2.6 percent of the total volatile organic compound emissions, 

respectively, within a 10-mile radius of the airports terminal area 

and that nonairport sources were considerably more important to local 

air quality than aircraft.[Footnote 37] In addition, a 2001 report on 

an air quality initiative for Boston Logan International Airport stated 

that the airport contributed less than 1 percent of the ozone-forming 

nitrogen oxides and volatile organic compound emissions in the Boston 

area.[Footnote 38]



Little research has been done on how much of total area emissions 

(called an emissions inventory) are attributable to ground support 

equipment and airport-related road traffic, because they are 

categorized as nonroad and onroad mobile sources, both of which are 

already accounted for in emissions inventories. However, our analysis 

of the Dallas/Fort Worth International Airport emissions inventory 

indicated that ground support equipment contributed almost 3 percent of 

the nitrogen oxide emissions for the area. When all airport-related 

emissions are added together, we estimated that the Dallas/Fort Worth 

International Airport was responsible for 6 percent of nitrogen oxides 

in the metropolitan area.[Footnote 39]



The amount of emissions attributable to each source varies by airport. 

According to a 1997 study of four airports,[Footnote 40] ground access 

vehicles were the most significant source of mobile emissions, 

responsible for 45 to 68 percent of the airports volatile organic 

compounds and 27 to 63 percent of the nitrogen oxides emitted from 

mobile sources.[Footnote 41] Aircraft operations were found responsible 

for the next largest share of emissions from mobile sources, with total 

contributions of 15 to 38 percent and 26 to 37 percent for volatile 

organic compounds and nitrogen oxides, respectively. Ground support 

equipment accounted for 12 to 13 percent of total emissions from 

volatile organic compounds and 14 to 20 percent of total nitrogen 

oxides from mobile sources at the airports. The report also found that 

auxiliary power units for aircraft contributed a small amount of the 

emissions from volatile organic compounds and 9 to 20 percent of total 

nitrogen oxide emissions from mobile sources. According to the report, 

data on particulate matter emissions is not available for aircraft and 

auxiliary power units, but ground access vehicles contribute one type 

of particulate matter at 1.3 to 2.7 the rate emitted by ground support 

equipment.



Health and Environmental Impact of Pollutants:



Some pollutants associated with aviation activities can increase the 

risk of a variety of health and environmental impacts. However, 

attributing these impacts to any particular source is extremely 

difficult because of the multiplicity of pollution sources in urban 

areas and the complexities involved in determining the exact causes of 

disease and environmental damage. The limited amount of research 

available indicates that the impact of the pollutants associated with 

airport activities is no more pronounced in the areas near airports 

than it is in other urban areas. Nevertheless, the cumulative impact of 

pollution from all sources can affect health and the environment.



The pollutant of most concern in the United States and other industrial 

countries is ozone, which is formed when nitrogen oxides, some types of 

volatile organic compounds, and other chemicals are combined and heated 

in the presence of light in the atmosphere. Ozone been shown to 

aggravate respiratory aliments, such as bronchitis and asthma. Research 

has indicated that certain levels of ozone affect not only people with 

impaired respiratory systems, but healthy adults and children as well. 

Exposure to ozone for several hours at relatively low concentrations 

has been found to significantly reduce lung function and induce 

respiratory inflammation in normal, healthy people during 

exercise.[Footnote 42]



In addition, according to EPA, there is growing public concern over 

emissions of air toxics, which include benzene, formaldehyde, and 

particulate matter, because of their potential adverse effects on 

health. Some of these emissions are associated with aviation 

activities. EPAs 1996 National Toxics Inventory indicates that amounts 

of hazardous air pollutants produced by aircraft are small relative to 

other sources such as on-road vehicles. However, EPAs national 

estimates are based on limited data, and very little data is available 

on toxic and particulate matter emissions in the vicinity of airports. 

A study of emissions at Los Angeles International Airport is expected 

to shed some light on the subject. In addition, FAA is involved in a 

study on identifying methods to measure aircraft particulate matter 

emissions.



In the upper atmosphere, aircraft emissions of carbon dioxide and other 

greenhouse gases can contribute to climate change. Greenhouse gases can 

trap heat, potentially increasing the temperature of the earths 

surface and leading to changes in climate that could result in such 

harmful effects as coastal flooding and the melting of glaciers and ice 

sheets. According to a 1999 report by the Intergovernmental Panel on 

Climate Change, conducted under the auspices of the United Nations, 

global aircraft emissions in general accounted for approximately 3.5 

percent of the warming generated by human activities.[Footnote 43] Jet 

aircraft are also the largest source of emissions generated by human 

activity that are deposited directly into the upper atmosphere. Carbon 

dioxide is the primary aircraft emission; it survives in the atmosphere 

for over 100 years and contributes to climate change. In addition, 

other gases and particles emitted by jet aircraft including water 

vapor, nitrogen oxides, soot, contrails, and sulfate combined with 

carbon dioxide can have two to four times as great an effect on the 

atmosphere as carbon dioxide alone, although some scientists believe 

that this effect requires further study. The Intergovernmental Panel on 

Climate Change concluded that aircraft emissions are likely to grow at 

3 percent per year and that the growing demand for air travel will 

continue to outpace emission reductions achieved through technological 

improvements, such as lower emitting jet engines.



Table 6 summarizes the possible environmental effects of the major 

pollutants associated with aviation related activities on the human 

health and the environment.



Table 6: Health and Environmental Effects of Air Pollutants:



Pollutant: Ozone; Health effects: Lung function impairment, effects on 

exercise performance, increased airway responsiveness, increased 

susceptibility to respiratory infection, increased hospital admissions 

and emergency room visits, pulmonary inflammation, and lung structure 

damage (long term).; Environmental effects: Crop damage, damage to 

trees, and decreased resistance to disease for both crops and 

ecosystems.



Pollutant: Carbon monoxide; Health effects: Cardiovascular effects, 

especially in those persons with heart conditions.; Environmental 

effects: Adverse health effects on animals similar to effects on 

humans.



Pollutant: Nitrogen oxides; Health effects: Lung irritation and lower 

resistance to respiratory infections.; Environmental effects: Acid 

rain, visibility degradation, particle formation, contribute toward 

ozone formation, and act as a greenhouse gas in the atmosphere and, 

therefore, may contribute to climate change.



Pollutant: Particulate matter; Health effects: Premature mortality, 

aggravation of respiratory and cardiovascular disease, changes in lung 

function and increased respiratory symptoms, changes to lung tissues 

and structure, and altered respiratory defense mechanisms.; 

Environmental effects: Visibility degradation, damage to monuments and 

buildings, safety concerns for aircraft from reduced visibility.



Pollutant: Volatile organic compounds; Health effects: Eye and 

respiratory tract irritation, headaches, dizziness, visual disorders, 

and memory impairment.; Environmental effects: Contribute to ozone 

formation, odors, and have some damaging effect on buildings and 

plants.



Pollutant: Carbon dioxide, water vapor, and contrails; Health effects: 

None.; Environmental effects: Act as greenhouse gases in the atmosphere 

and, therefore, may contribute to climate change..



Pollutant: Sulfur dioxide; Health effects: Respiratory irritant. 

Aggravates lung problems, particularly for individuals with asthma.; 

Environmental effects: Causes damage to crops and natural vegetation. 

In presence of moisture and oxygen, sulfur dioxide converts to sulfuric 

acid, which can damage marble, iron, and steel.



[End of table]



Source: EPA and FAA.



[End of section]



Appendix III: Federal, State, and International Responsibilities for 

Controlling Aviation-related Emissions:



The federal government and the states have responsibility for 

regulating sources of aviation emissions under the Clean Air Act, which 

was established to improve and protect air quality for human health and 

the environment.[Footnote 44] In addition, a United Nations entity, the 

International Civil Aviation Organization (ICAO), establishes 

international aircraft emissions standards, studies aviation 

emissions-related issues, and provides guidance for controlling these 

emissions. ICAO includes 188 member countries, which have agreed to 

adopt, to the extent possible, standards set by ICAO.



For aircraft or aircraft engine emissions, the Clean Air Act gives EPA 

the authority[Footnote 45] to establish emission standards. EPA, in 

consultation with FAA, has chosen to adopt the international emissions 

standards established by ICAO. FAA serves as the United States 

representative to ICAOs Committee on Aviation Environmental 

Protection, which is responsible for assessing aviations impact on the 

environment and establishing the scientific and technological basis for 

new gaseous emissions standards for aircraft engines. The committee has 

established several working groups to identify and evaluate emissions-

reduction technology and operational measures and market-based options 

to reduce emissions. Both FAA and EPA participate in these working 

groups. In addition, FAA is responsible for monitoring and enforcing 

U.S. manufacturers compliance with aircraft emissions standards, which 

it does in part through its process for certifying new aircraft 

engines.



In addition, the federal government plays a role in developing 

technologies to reduce aircraft emissions. NASA, in partnership with 

the aviation industry and universities, conducts research into 

improving the capabilities and efficiency of commercial aircraft. Part 

of this effort includes developing more fuel efficient and lower 

emitting engines. Over the years, NASA has been credited with 

contributing to technologies that have significantly lowered the amount 

of fuel consumed by jet engines; this in turn has reduced some 

emissions, particularly the greenhouse gas, carbon dioxide.



Under the Clean Air Act, EPA has jurisdiction for establishing national 

standards for all other mobile sources of emissions, including those 

associated with airport operations--such as ground support equipment 

and ground access vehicles such as automobiles, trucks, and buses 

operating on airport property. In establishing these emissions 

standards, EPA is to take into consideration the time it takes to 

develop the necessary technology and the cost of compliance.



The Clean Air Act also directs EPA to establish national standards for 

ambient air quality, and these standards can affect airport operations 

and expansion plans. EPA has set National Ambient Air Quality Standards 

for carbon monoxide, lead, nitrogen dioxide, particulate matter, ozone, 

and sulfur dioxide. EPA has labeled them criteria pollutants because 

the permissible levels established for them are based on criteria or 

information on the effects on public health or welfare that may be 

expected from their presence. The criteria pollutants are directly or 

indirectly generated by multiple sources, including airport activities. 

Local areas not meeting the standards for criteria pollutants are 

referred to as nonattainment areas. The act groups nonattainment areas 

into classifications based on the extent to which the standards for 

each criteria pollutant are exceeded and establishes specific pollution 

controls and attainment dates for each classification. The act has set 

2010 as the deadline for extreme ozone nonattainment areas to meet the 

standards. (California is currently the only state with such an area).



The Clean Air Act also authorizes EPA to set ambient air quality 

standards; however, the states, which can adopt EPAs or their own more 

stringent standards, are responsible for establishing procedures to 

attain and maintain the standards. Under the act, states that have 

areas in nonattainment, must adopt plans--known as state implementation 

plans--for attaining and maintaining air quality standards and submit 

the plans to EPA for approval. State implementation plans are based on 

analyses of emissions from all sources in the area and computer models 

to determine whether air quality violations will occur. If data from 

these analyses indicate that air quality standards would be exceeded, 

the states are required to impose controls on existing emission sources 

to ensure that emissions do not exceed the standards. States can 

require control measures on airport emissions sources for which they 

are not preempted from regulating, such as power plants and ground 

access vehicles, and, to a limited extent, ground support 

equipment.[Footnote 46] However, states cannot control emissions from 

sources they are preempted from regulating including aircraft, marine 

vessels, and locomotives. If a state fails to submit or implement an 

adequate implementation plan, EPA can impose an implementation plan.



FAA is responsible for ensuring that its actions supporting airport 

development projects--such as providing funding for those projects--

comply with federal environmental requirements, including those 

pertaining to air quality. The National Environmental Policy Act of 

1969 sets forth a broad national policy intended to protect the quality 

of the environment. The act requires that federal actions receive an 

environmental review, which includes the impact on air quality, before 

federal decisions are made and actions are taken. For example, 

federally-funded proposals to construct airport runways require action 

by FAA. For airport projects, FAA is the lead agency responsible for 

the environmental reviews and for the approval of the airports 

proposed design. EPA examines the environmental review documents 

prepared by FAA and other federal agencies.



The general conformity rule of the Clean Air Act directs federal 

agencies, such as FAA to ensure that federal actions at airports not 

delay the attainment or maintenance of ambient air quality standards. 

Therefore, FAA must determine, usually as part of the environmental 

review, that the estimated amount of emissions caused by a proposed 

federal action at an airport comply with the state implementation plan 

for meeting the standards. FAA cannot approve an action unless it 

complies with the plan. In order to demonstrate compliance, the airport 

could be required to implement emission control measures, such as 

converting airport vehicles to alternative lower emitting fuels.



To help carry out its responsibilities under the Clean Air Act and the 

National Environmental Policy Act, FAA developed the Emissions and 

Dispersion Modeling System, which is a computer model that estimates 

the amount and type of emissions from airport activities. FAA, 

airports, and others use the model to assess the local air quality 

impacts of airport development projects. Typically, the model is used 

to estimate the amount of emissions produced by aircraft, ground 

support equipment, and other sources operating at the airport or in the 

nearby vicinity. The model also reflects the way these airport 

emissions are dispersed in the atmosphere due to wind and other 

factors. The dispersion analysis is intended to assess the 

concentrations of the emissions at or near the airport and, thereby, 

help to indicate the effect of the emissions on local air quality.



FAA is also engaged in several research projects to improve the 

understanding of aircraft emissions and methods for quantifying them. 

For example, FAA is working with the Society of Automotive Engineers to 

develop a protocol for measuring particulate matter emissions from 

aircraft. FAA is also studying ways to increase the accuracy of 

aircraft emission dispersion models and is analyzing the air quality 

impact of aircraft operations at or above 3000 feet.



[End of section]



Appendix IV: Efforts by Three States to Reduce Aviation-related 

Emissions:



Three states with major commercial airports in nonattainment areas--

California, Texas, and Massachusetts--have targeted airports for 

emissions reductions.



California:



California has more major commercial airports--seven--than any other 

state, and all of them are located in nonattainment areas for ozone. 

Although none of the airports are a major source of ozone precursors 

such as nitrogen oxides and volatile organic compounds, California air 

quality authorities have turned their attention to airports as a source 

of reductions needed to reach and maintain attainment of ozone 

standards because they believe they have exhausted other sources, 

including large sources such as power plants and small sources like 

lawn mowers. The Los Angeles region is the only one in the country 

classified as an extreme nonattainment area for ozone. According to 

state environmental officials, emissions from all airport 

activities[Footnote 47] contributed about 1 to 2 percent of the 

pollution in the Los Angeles region in 2000, and this is projected to 

increase to nearly 4 percent by 2020. State environmental officials 

attribute this projected increase in the airports ozone contribution 

to an expected doubling of aircraft emissions coupled with a 50 percent 

decrease in emissions from other sources. These projections do not take 

into account the reductions in aircraft activity as a result of the 

events of September 11, 2001, and the financial uncertainties of the 

airline industry.



Because of the severity of the nonattainment level in the Los Angeles 

area, the state requires reductions from all sources, including 

airports, by 2010. Along with Los Angeles local air quality agency, 

the California Air Resources Board has negotiated with EPA and airlines 

for a memorandum of understanding for voluntary emission reductions 

from ground support equipment.[Footnote 48] According to California Air 

Resources Board officials, emission reductions would be achieved by 

replacing older, high polluting ground support equipment with new 

cleaner gas and diesel fueled equipment or equipment operating with 

alternative energy sources, such as electricity. In doing so, the 

officials expect an 80 percent reduction of emissions from ground 

support equipment that are used at five airports--Los Angeles 

International, Burbank, Ontario International, Long Beach, and John 

Wayne--in the Los Angeles region by 2010.



Californias efforts to cut emissions from ground support equipment in 

the Los Angeles area are part of an aggressive statewide campaign to 

reduce airport pollution. In addition to using its limited authority 

under the Clean Air Act to implement airport related emissions 

reductions, the state has also established criteria for issuing air 

quality certifications provided for in federal law.[Footnote 49] Under 

this law, before federal funds are allocated for projects involving a 

new airport, a new runway, or a major runway extension, the state 

governor must certify that there is reasonable assurance that the 

project will be located, designed, constructed, and operated in 

compliance with applicable air and water quality standards. The state 

has developed a unique set of criteria for determining whether a 

proposed airport expansion project would have an impact on the 

environment. If the project exceeds one of the criteria, the airport is 

required to implement emissions mitigation measures in order to attain 

certification. For example, the certification for a runway project was 

invoked when the Sacramento International Airport planned to increase 

the number of parking spaces. The criteria on which the certification 

was based included annual increases of more than 7 million passengers 

or 139,000 aircraft operations (i.e., landings and takeoffs) or a 

permanent increase of more than 4,200 parking spaces. The airports 

plans exceeded the number of parking spaces and, as a result, were 

required to implement emission mitigation measures in order to build 

the parking spaces. According to state officials, California is the 

only state to develop such criteria for certifying airport expansion 

projects. As of December 2002, three airports in California--Sacramento 

International, San Jose International, and Ontario International--have 

initiated expansion projects that required state certification.



Texas:



Texas has four regions in nonattainment of national air quality 

standards for ozone, but the Houston and Dallas/Fort Worth regions have 

required the most extensive emission control measures for reaching 

attainment. These two regions contain the states four largest 

airports--Dallas/Fort Worth International, Dallas Love Field, George 

Bush International/ Houston, and Houston Hobby--all of which are among 

the nations 50 busiest airports. The Houston area has one of the worst 

ozone problems in the country and has been designated as a severe 

nonattainment area, requiring substantial control measures in order to 

comply with the Clean Air Act. Dallas-Fort Worth, on the other hand, 

has a much less serious ozone problem but has been penalized by EPA for 

not meeting its attainment schedule. EPA classified the Dallas/Fort 

Worth region as a moderate ozone nonattainment area in the early 1990s, 

which meant that the region was required to demonstrate attainment of 

the 1-hour ozone standard[Footnote 50] by November 1996. However, air 

quality data from the region showed that the area failed to meet the 

attainment goal in 1996, which resulted in EPA reclassifying the 

severity level of the region from moderate to serious. The downgrading 

of the Dallas regions classification forced state and local 

authorities to develop a new state implementation plan with more 

extensive control measures. The states environmental agency, the Texas 

Natural Resource Conservation Commission[Footnote 51], included 

emissions from airport activities among the top ten highest sources of 

nitrogen oxides emissions from nonroad mobile sources in both the 

Dallas-Fort Worth and Houston regional areas.



Noting that the emissions inventories for both Houston and Dallas-Fort 

Worth placed airports in the top 10 sources for nitrogen oxide 

emissions of nonroad mobile sources, which contribute to ozone 

formation, the Texas Natural Resource Conservation Commission 

determined that control measures for each area were warranted. For 

Dallas-Fort Worth, the commission revised the state implementation plan 

for the area to include reduction of nitrogen oxide emissions from 

ground support equipment at both major commercial airports in the area-

-Dallas/Forth Worth International and Dallas Love Field. The plan 

called for a 90 percent reduction of nitrogen oxide emissions from 

ground support equipment by 2005. The airline industry challenged the 

state rule by filing a lawsuit, citing the Clean Air Acts preemption 

rule, which it argued prohibited states and local authorities from 

regulating ground support equipment. The lawsuit was dropped in October 

2000 when the commission, the cities of Dallas and Fort Worth (which 

operates the major airports), and the affected airlines--American, 

Delta, and Southwest--reached a voluntary agreement to achieve a 90 

percent reduction in nitrogen oxide emissions attributable to ground 

support equipment or other equipment by 2005. The commission brokered a 

similar agreement with the city of Houston as its operator of the 

airports and the affected airlines. Under both the Dallas/Fort Worth 

and Houston agreements, the affected carriers voluntarily agreed to 

reductions equivalent to 75 percent of nitrogen oxides emitted from 

ground service equipment and the cities--Dallas-Forth Worth, and 

Houston--as the operators of the airports agreed to be responsible for 

the remaining 15 percent to achieve the 90 percent reduction.



Massachusetts:



The Boston area is classified as a serious ozone nonattainment area and 

state environmental officials are under increasing pressure by 

citizens, community groups, and industry to control emissions from 

Bostons Logan International Airport. State environmental officials 

have estimated that while only a small amount of total nitrogen oxide 

emissions in the area are attributable to aircraft, these emissions 

will continue to increase. They estimate that other emission sources at 

the airport, such as ground support equipment, will eventually begin to 

decrease as they are replaced by lower polluting equipment. The Boston 

airport is also consistently ranked as the airport with the second 

highest number of air travel delays in the nation. These air travel 

delays add to regional air quality problems because idling aircraft 

contribute to pollution. To meet a growing travel demand, Boston 

airport officials have proposed building a new runway to allow the 

airport to improve operating efficiency, thereby reducing emissions 

from idling aircraft. As part of this proposal, the airport also agreed 

that emissions would not exceed 1999 levels.



To address airport operation delays and reduce emissions, airport 

officials have considered three strategies--peak period pricing, 

emissions credit trading, and reducing emissions from ground support 

equipment.[Footnote 52] Peak period pricing is a demand management 

strategy that raises landing fees during designated air traffic peak 

hours, which is expected to induce some air carriers to discontinue or 

reduce operations during peak periods. With fewer aircraft waiting to 

taxi and land during peak periods, emissions from aircraft would be 

reduced and regional air quality would be improved. An emissions credit 

trading program is designed to allow facilities to meet emission 

reduction goals by trading and transferring air emission credits with 

emission sources that surpassed their allotted targets. Used by EPA to 

reduce pollutants that contribute to acid rain, the emission credit 

trading program allows sources, such as industry, the flexibility to 

meet their reduction obligations in a more cost effective manner. 

Because emission credits are considered additional or surplus to 

those that are regulated and otherwise reduced under federal and state 

laws, they aid in achieving an overall decline in emissions regionwide, 

according to Boston airport officials. Similar to situations at the 

major airports in both California and Texas, state and airport 

officials have also focused on reducing emissions from ground support 

equipment.



In the wake of the events of September 11, 2001, which resulted in a 

reduction of flights and emissions at the Boston airport, the airports 

operator--Massachusetts Port Authority--believes that peak pricing and 

emissions trading will not be needed to keep emissions below 1999 

levels for several years. The Port Authority, however, continues to 

work with airport tenants to implement voluntary emission reduction 

strategies. In addition, in an August 2002 Record of Decision approving 

plans for a new runway and taxiways, FAA directed the Port Authority to 

develop and submit a plan for peak period pricing or other demand 

management strategies to reduce delays, which the Port Authority had 

committed to complete this plan as part of the state environmental 

review process, before initiating construction. In the Record of 

Decision, FAA pointed out that the program would have to comply with 

applicable federal constitutional and other requirements.



[End of section]



Appendix V: Airports and Airlines Efforts To Reduce Emissions:



Many of the nations busiest airports, in conjunction with air 

carriers, have voluntarily implemented control measures to reduce 

emissions by activities that include modifying the operating procedures 

of aircraft, using alternative fuels to run ground support equipment, 

and reducing the number of passenger vehicles entering and exiting the 

airport.



Aircraft:



Although airports have no control over emissions from aircraft, they 

can encourage air carriers to reduce emissions as much as possible 

through modified operating procedures. For example, limiting the number 

of running engines during taxiing of aircraft can reduce the emission 

of nitrogen oxides and volatile organic compounds. According to airport 

officials at the Boston Logan International Airport, some pilots use 

single-engine taxiing with some aircraft to reduce emissions. Another 

example is reducing the use of engine reverse thrust to slow an 

aircraft to taxi speed after it lands. This procedure reduces nitrogen 

oxide emissions, but it may occur at the expense of slightly higher 

emissions of volatile organic compounds if the taxi time is increased 

because a runway turnoff is missed. Many factors are involved in the 

decision to use reverse thrust, including runway length and width, 

runway surface and taxiway conditions, weather conditions, and aircraft 

type.



Modifying the operating procedures of aircraft does not require 

additional equipment or aircraft modifications, but it is done at the 

discretion of the pilot. Under federal regulations, the commanding 

pilot of the aircraft is responsible for the safety of the passengers, 

crewmembers, cargo, and the airplane, and any procedure that modifies 

aircraft operation is at the discretion of the pilot. In addition, 

modifications to operating procedures may not be feasible in all 

weather conditions, with all aircraft, and/or at all airports.



Ground Support Equipment:



Most ground support equipment used by air carriers at airports is 

fueled by gasoline or diesel. Replacing that equipment with cleaner-

burning gas or diesel engines or equipment powered by alternative 

fuels--such as electricity, liquefied petroleum gas, and compressed 

natural gas--could result in reduced emissions. A reliable and 

comprehensive database of the ground support equipment in use does not 

exist; however, according to FAA, there are about 72,000 pieces of such 

equipment in operation. The Air Transport Association estimated that of 

the pieces of ground support equipment in used in 1999, about 30 to 40 

percent operate on diesel fuel; 50 to 60 percent operate on gasoline; 

and about 10 percent use alternative fuels. Several airports we 

visited, including Los Angeles International, Sacramento 

International, Dallas/Fort Worth International, Boston Logan 

International, and Atlanta Hartsfield, provided air carriers with the 

infrastructure necessary to operate alternatively fueled ground support 

equipment, and some carrier have begun converting their fleets of 

ground support equipment to alternative fuels. Los Angeles 

International, for instance, provided a varied alternative fuel 

infrastructure, including both compressed and liquefied natural gas 

refueling stations and electric charging stations, which offered air 

carriers different options to use alternative fueled equipment. Airport 

officials told us that air carriers have been using the alternative 

fuel stations to refuel their ground support equipment.



FAA reported[Footnote 53] that replacing conventionally-fueled ground 

support equipment with alternatively-fueled equipment is the most cost 

effective way to reduce emissions at airports. Additionally, equipment 

originally designed to use the alternative fuels has less impact on the 

environment than equipment that is converted from using a conventional 

fuel to an alternative fuel; however, it is also more costly up front, 

and alternative fuel technology does not currently exist for some types 

of ground support equipment. Airports and air carriers use about 24 

different types of ground support equipment, such as cargo loaders, 

aircraft pushback tractors, baggage tugs, and service trucks; and 

according to aviation industry officials, conversion of equipment from 

conventional to alternative fuel has had a mixed result in terms of 

operating the equipment. According to airline officials, liquefied 

petroleum and compressed natural gas vehicles require larger fuel tanks 

and are harder to operate; the cost for the alternative fuel 

infrastructure engines for ground support equipment is also very 

expensive. Air carriers and airports commonly have had to use a mixed 

fleet of liquefied petroleum and compressed natural gas and electric 

ground support equipment because of limitations of the various types of 

alternative fuel sources. For example, electricity has not been 

sufficiently powerful to run some of the ground service equipment that 

bear significant loads. In addition, some types of electric equipment 

do not work well in cold weather conditions. According to the Air 

Transport Association, for these and other reasons, no one equipment 

size or type fits all airlines needs.



Providing Electric Power at Gates:



A trend at airports is to provide electricity and air conditioning 

service for aircraft at the gates, which can permit a reduction in the 

use of aircraft auxiliary power units and thereby reduce emissions, 

according to FAA. Airports are not required to install boarding gates 

that provide electricity to parked aircraft, but an FAA report notes 

that some airports have been proactive in reducing emissions and have 

invested in these electric gates.[Footnote 54] The report explains that 

electric gates operate at greater energy efficiency than auxiliary 

power units, which support aircraft with power and ventilation systems 

when they are parked at the gates, and can substantially reduce 

emissions. Many airports, including Los Angeles International, 

Sacramento International, Dallas/Fort Worth International, and Boston 

Logan International provide electric power for parked aircraft, which 

allows aircraft to turn off their auxiliary power units while 

maintenance and cleaning crews prepare the aircraft for the next 

flight. However, air carriers are not required to use the electric 

gates, and some chose not to use them because they hinder the 

efficiency of their operations. For instance, one airline that 

specializes in getting its aircraft into and out of airports quickly--

in 20 minutes or less--rarely uses the electricity provided by the 

airport, instead running the auxiliary power unit the entire time 

aircraft are at the gate, according to officials of that airline. These 

officials note that electric gates are only useful for those aircraft 

that are parked for 30 to 45 minutes or longer before they take off 

because of the time it takes to hook the aircraft up to the system.



Passenger Vehicles:



Although EPA already regulates emissions from most passenger vehicles 

and trucks, options are available to further reduce emissions from 

theses sources at airports. Vehicles making trips to and from airports 

include employee and private passenger vehicles, airport and tenant-

owned fleet vehicles, public transport vehicles and shuttles, and cargo 

vehicles for deliveries. All the airports we visited have implemented 

or are in the process of implementing emission reduction efforts for 

this emissions source. Some emission reduction measures that airports 

have applied to such ground access vehicles include the following:



* Dallas/Fort Worth International airport has consolidated its rental 

car facilities and, according to airport officials, the consolidation 

effort has reduced rental car related emissions by 95 percent. In 

addition, the single shuttle service that resulted from consolidating 

the rental car facilities uses alternative fuel shuttles. George Bush 

Intercontinental/Houston plans to consolidate its rental car 

facilities; and Los Angeles International, Atlanta Hartsfield, and 

Boston Logan International are also considering the option.



* Dallas/Fort Worth International, Los Angeles International, and 

Sacramento International all have promoted some kind of employee/tenant 

commuter rideshare program. According to Los Angeles International 

Airport officials, about 25 percent of airport employees participate in 

a commuter rideshare program.



* Los Angeles International restructured its airport shuttle-van 

program in 1999 by reducing the number of shuttle vans authorized to 

make passenger pickups at the airport and requiring them to phase-in 

alternative fuel vehicles into their fleets. The airport expects all of 

the authorized operators to use alternative fuel vehicles by 2003. The 

airport is also considering requiring taxicabs serving the airport to 

operate on natural gas.



* Both Chicago OHare International and Dallas/Fort Worth International 

airports have built an electric automated transport system, also known 

as a people mover, within the airport property to transport 

passengers between terminals. Chicago OHare International airport also 

offers direct rail service to the city center and provides alternative 

transportation to passengers and airport employees entering/exiting the 

airport. Los Angeles International provides alternative public 

transportation with a bus service that travels between the airport and 

the park-and-ride station at the Van Nuys Airport.



Other Measures:



Airports have also reduced emissions from other sources, such as their 

on-site utilities plants. Los Angeles International airports central 

utilities plant operates under a cogeneration energy saving system, 

which simultaneously generates electrical power and steam. Some 

electrical power is sold to the local electric company, and the steam 

provides heating and air conditioning (by powering steam refrigeration 

chillers) for the airports buildings and central terminal area. 

According to airport officials, Los Angeles International receives more 

than $3 million in emissions credit each year for the emission controls 

achieved with its central utilities plant. Dallas/Fort Worth 

International airport also generates electricity with its solar power 

generators, which produce lower emissions than traditional powered 

generators. Airport officials stated that they have the capacity to 

build cogeneration plants using solar power and sell the power/surplus 

electricity to the state as well. The airport is trying to negotiate 

with federal agencies to receive credits for the amount of emission 

reductions achieved by using solar power energy and selling surplus 

electricity to the state. If successful, the airport could use these 

credits to gain approval of future expansion projects that increase 

emissions.



[End of section]



Appendix VI: Overview of Aircraft Fuel, Noise, and Nitrogen Oxide 

Reduction Technologies:



Fuel efficiency improvements involve every aspect of an aircrafts 

design. Traditionally, about 40 percent of the improvements have come 

from airframe improvements and 60 percent from propulsive and engine 

improvements. Airframe improvements include improving the aerodynamic 

shape and structural efficiency (for example, reduced aircraft weight). 

Propulsive improvements have primarily resulted from increasing the 

size of the bypass fan and improving the shape of the bypass fan 

blades. Engine improvements have centered on increasing the pressure of 

the air that goes through the engine core (the engine operating 

pressure). The increased engine operating pressures allow more work to 

be extracted from a unit of fuel, thereby improving fuel consumption.



One of the first major technology breakthroughs with commercial jet 

engines occurred in the mid-1960s with the introduction of the turbofan 

jet engine (see figure 3). This design uses a bypass fan in front of 

the jet engine core to move much of the propulsive air and bypass the 

core of the jet that contains the compressor, combustor, and turbine. 

The primary motivation for this advancement was increased fuel 

efficiency. However, the reduced noise of this new design was an 

additional benefit. Noise was reduced because the bypass air moves at a 

slower speed than the air going through the core. Further noise 

reductions have evolved over time by increasing the size of the bypass 

fans and improving the shapes of the bypass fan blades. Researchers at 

NASA have indicated they are facing diminishing returns as they seek to 

reduce noise by further improving bypass fans and aircraft surfaces. 

They are also exploring more advanced technologies such as using 

electronics to actively control noise.



Figure 3: Major Components of a Turbofan Engine (Two-Shaft High Bypass 

Engine):



[See PDF for image]



[End of figure]



NASA, in association with jet engine manufacturers and the academic 

community, is working on several technologies to reduce nitrogen oxide 

emissions. NASAs research to reduce nitrogen oxide emissions is a 

component of its Ultra Efficient Engine Technology Program. The goal of 

this program is to develop technologies that will enable U.S. 

manufacturers to compete in the global marketplace for new commercial 

gas turbine engines. An important aspect of this program is reducing 

jet engine emissions of nitrogen oxides. NASA has set what it considers 

ambitious goals[Footnote 55] for its nitrogen oxide reduction research. 

These goals include the following:



* Demonstrate combustion technology, in a NASA test laboratory, that 

will reduce nitrogen oxides 70 percent relative to todays standard. 

This equates to a 20-50 percent reduction compared with the best 

engines being produced today.



* Demonstrate these technologies in engine combustor components by 

2005.



* Hand off the technologies to manufacturers in a timely fashion so 

they can be incorporated in new engines in the 2007-2010 time frame.



* Study long-term concepts that could greatly reduce or eliminate 

nitrogen oxides emissions in the 2025-2050 time frame.



According to representatives from jet engine manufacturers, nitrogen 

oxide reduction research is complex and time consuming and requires 

specialized and expensive test equipment. They also said that basic 

research needed to understand the formation of nitrogen oxides in jet 

engines and to make significant changes to current engine designs is so 

expensive and lacking in marketplace investment rewards that no 

significant or sustained basic research in this area would take place 

without NASA taking the lead.



Adding to the complexities of this research is the extreme variation in 

jet engine designs. Other research and development by NASA and engine 

manufacturer is constantly raising engine-operating pressures as a way 

of improving fuel consumption and reducing greenhouse gas emissions. 

However, these developments tend to increase nitrogen oxide emissions, 

and further modifying engine designs to reduce nitrogen oxides has a 

direct impact on every other aspect of engine design: safety, 

operability, service life, operating costs, maintenance costs, and 

production costs. Jet engine manufacturers are taking divergent design 

approaches as they research how to maintain these other high-priority 

design characteristics while reducing nitrogen oxide emissions. As a 

result, NASA divides its resources over numerous projects.



NASAs Ultra Efficient Engine Technology Program is scheduled to 

complete research and technology on aircraft engine combustor 

refinements that reduce the formation of nitrogen oxides so that the 

refinements can be introduced on aircraft by 2010. Because of the 30-

year projected life of commercial aircraft, it could take decades 

before enough lower emitting aircraft are introduced in the commercial 

fleet to contribute to significant reductions in nitrogen oxides. 

NASAs nitrogen oxides research under the Ultra Efficient Engine 

Technology Program is centered on developing lean-burning rather than 

rich burning combustors that are in commercial service today. These 

lean-burning combustors will increase fuel/air mixing rates that, when 

combined with the lean fuel/air ratios, will reduce temperatures 

locally in the combustor and thus reduce the nitrogen oxide emissions 

generated. Because of funding constraints, NASA does not plan to 

implement the next phase of development, which is to examine the 

combustor improvements in a full engine test environment. NASA is 

relying on the engine manufacturers to implement this full engine 

development. Both NASA and aviation industry engineers said that this 

full engine development phase will be far more complex and involve many 

more design trade-offs than the combustor development phase. 

Additionally, they acknowledged that some of the nitrogen oxide 

reductions achieved during the combustor development phase would be 

lost during the full engine development phase. NASA researchers 

indicated these losses could be particularly severe because engine 

manufacturers are concurrently making other design changes to their 

engines to minimize fuel consumption and these changes will increase 

nitrogen oxide emissions. Consequently, NASA researchers are not sure 

how many of the improvements they expect to achieve by 2005 will 

survive as the engine manufacturers take over responsibility for 

completing the development of these improvements in a full engine test 

environment and then integrate these improvements into production-ready 

engines.



NASA is also working on a long-term revolutionary jet engine design 

that could significantly reduce all emissions including nitrogen oxides 

while also reducing fuel consumption. Under its intelligent 

propulsions controls design concept, engine functions are more 

precisely controlled using computers. For example, with this design, 

the number of ports delivering fuel to the engine combustion chamber 

would be greatly increased, and each port would be computer controlled. 

NASA officials are optimistic about the potential of this concept, but 

they added that research is in the early stages and that it will 

probably take 20 years or more to develop. NASAs overall long-term 

research plan calls for spending about $20 million per year over the 

next 5-year period to explore improved fuel burned and nitrogen oxide 

emission reduction technologies.



NASA researchers are also studying the possibility of developing zero 

emissions (except water) hydrogen-fueled aircraft with an electric 

propulsion system. While they note that there would have to be many 

breakthroughs in hydrogen storage and fuel cell technologies and high-

powered lightweight electric motors before a hydrogen-fueled commercial 

airliner is feasible, they believe many of the needed breakthroughs 

could occur in the next 50 years.



NASA[Footnote 56] is also researching nonengine methods that will 

indirectly reduce nitrogen oxides (and all other emissions) by reducing 

fuel consumption. This work includes more efficient airframes through 

aerodynamic improvements, structural improvements (i.e., reducing 

aircraft weight), and operational efficiencies (i.e., more fuel 

efficient flight routes, reduced taxi time). Historically, 40 percent 

of aviation fuel improvements have come from such efficiency 

improvements. Aviation emission experts emphasize that it is important 

that research into these types of improvements continue along with the 

engine research. The advantage of these improvements is that all 

emissions are reduced simultaneously without having to make emission 

trade-offs.



[End of section]



Appendix VII: Additional Information on Our Analysis of Aircraft 

Emissions:



Using the Emissions and Dispersion Modeling System (version 4.01) 

computer model developed by FAA and fleet data obtained from AvSoft, we 

calculated the landing/takeoff emissions for every aircraft model and 

engine combination in the U.S. commercial aircraft fleet during 2001. 

(See appendix I for additional information on our methodology.) Tables 

7 and 8 provide additional information on our comparison of older and 

newest model Boeing 737s. As shown below, older model Boeing 737s, 

produced in 1969-1998, averaged 12.1 pounds of nitrogen oxides per 

landing/takeoff (see table 7), while the newest model Boeing 737s, 

produced in 1997-2201, averaged 17.9 pounds of nitrogen oxides per 

landing/takeoff (see table 8). Tables 9, 10, and 11 provide additional 

information about the calculations and commercial fleet for data 

presented earlier in this report.



Table 7: Emission Information for Older Boeing 737s during Landing/

Takeoff:



Model: 737-200; Engine: JT8D-15; Pounds

NOx per LTO[A]: 13.361; Pounds CO

per LTO[A]: 9.912; Pounds VOC

per LTO[A]: 1.296; Number

in U.S. fleet in 2001: 55; Number

of LTOs in 2001: 101,887; Oldest in fleet: 1977; Newest

in fleet: 1985; Average

number

of seats: 113.1; Pounds takeoff

weight: 105000.



Model: 737-200; Engine: JT8D-15A; Pounds

NOx per LTO[A]: 11.835; Pounds CO

per LTO[A]: 10.475; Pounds VOC

per LTO[A]: 1.479; Number

in U.S. fleet in 2001: 65; Number

of LTOs in 2001: 85,577; Oldest in fleet: 1980; Newest

in fleet: 1988; Average

number

of seats: 113.7; Pounds takeoff

weight: 105000.



Model: 737-200; Engine: JT8D-17; Pounds

NOx per LTO[A]: 14.804; Pounds CO

per LTO[A]: 9.574; Pounds VOC

per LTO[A]: 1.165; Number

in U.S. fleet in 2001: 21; Number

of LTOs in 2001: 31,620; Oldest in fleet: 1976; Newest

in fleet: 1987; Average

number

of seats: 106.6; Pounds takeoff

weight: 105000.



Model: 737-200; Engine: JT8D-17(Q); Pounds

NOx per LTO[A]: 14.804; Pounds CO

per LTO[A]: 9.574; Pounds VOC

per LTO[A]: 1.165; Number

in U.S. fleet in 2001: 1; Number

of LTOs in 2001: 879; Oldest in fleet: 1976; Newest

in fleet: 1976; Average

number

of seats: 128.0; Pounds takeoff

weight: 105000.



Model: 737-200; Engine: JT8D-17A; Pounds

NOx per LTO[A]: 12.801; Pounds CO

per LTO[A]: 10.421; Pounds VOC

per LTO[A]: 4.204; Number

in U.S. fleet in 2001: 5; Number

of LTOs in 2001: 8,632; Oldest in fleet: 1983; Newest

in fleet: 1985; Average

number

of seats: 117.0; Pounds takeoff

weight: 105000.



Model: 737-200; Engine: JT8D-7B; Pounds

NOx per LTO[A]: 11.207; Pounds CO

per LTO[A]: 10.424; Pounds VOC

per LTO[A]: 2.326; Number

in U.S. fleet in 2001: 1; Number

of LTOs in 2001: 181; Oldest in fleet: 1969; Newest

in fleet: 1969; Average

number

of seats: 56.0; Pounds takeoff

weight: 100000.



Model: 737-200; Engine: JT8D-9A; Pounds

NOx per LTO[A]: 12.079; Pounds CO

per LTO[A]: 10.591; Pounds VOC

per LTO[A]: 2.042; Number

in U.S. fleet in 2001: 55; Number

of LTOs in 2001: 128,673; Oldest in fleet: 1968; Newest

in fleet: 1988; Average

number

of seats: 114.5; Pounds takeoff

weight: 100000.



Model: 737-200C; Engine: JT8D-15; Pounds

NOx per LTO[A]: 13.361; Pounds CO

per LTO[A]: 9.912; Pounds VOC

per LTO[A]: 1.296; Number

in U.S. fleet in 2001: 1; Number

of LTOs in 2001: 2,139; Oldest in fleet: 1974; Newest

in fleet: 1974; Average

number

of seats: 111.0; Pounds takeoff

weight: 105000.



Model: 737-200C; Engine: JT8D-17; Pounds

NOx per LTO[A]: 14.804; Pounds CO

per LTO[A]: 9.574; Pounds VOC

per LTO[A]: 1.165; Number

in U.S. fleet in 2001: 7; Number

of LTOs in 2001: 17,428; Oldest in fleet: 1979; Newest

in fleet: 1984; Average

number

of seats: 111.1; Pounds takeoff

weight: 105000.



Model: 737-200C; Engine: JT8D-17A; Pounds

NOx per LTO[A]: 12.801; Pounds CO

per LTO[A]: 10.421; Pounds VOC

per LTO[A]: 4.204; Number

in U.S. fleet in 2001: 5; Number

of LTOs in 2001: 12,750; Oldest in fleet: 1983; Newest

in fleet: 1985; Average

number

of seats: 111.6; Pounds takeoff

weight: 105000.



Model: 737-200C; Engine: JT8D-9A; Pounds

NOx per LTO[A]: 12.075; Pounds CO

per LTO[A]: 10.590; Pounds VOC

per LTO[A]: 2.042; Number

in U.S. fleet in 2001: 1; Number

of LTOs in 2001: 3,373; Oldest in fleet: 1980; Newest

in fleet: 1980; Average

number

of seats: 112.0; Pounds takeoff

weight: 100000.



Model: 737-300; Engine: CFM56-3B-1; Pounds

NOx per LTO[A]: 10.720; Pounds CO

per LTO[A]: 19.197; Pounds VOC

per LTO[A]: 1.201; Number

in U.S. fleet in 2001: 380; Number

of LTOs in 2001: 842,336; Oldest in fleet: 1984; Newest

in fleet: 1997; Average

number

of seats: 130.8; Pounds takeoff

weight: 122000.



Model: 737-300; Engine: CFM56-3B-2; Pounds

NOx per LTO[A]: 12.496; Pounds CO

per LTO[A]: 17.811; Pounds VOC

per LTO[A]: 0.991; Number

in U.S. fleet in 2001: 137; Number

of LTOs in 2001: 244,395; Oldest in fleet: 1984; Newest

in fleet: 1992; Average

number

of seats: 126.3; Pounds takeoff

weight: 122000.



Model: 737-300; Engine: CFM56-3C-1; Pounds

NOx per LTO[A]: 14.195; Pounds CO

per LTO[A]: 16.766; Pounds VOC

per LTO[A]: 0.859; Number

in U.S. fleet in 2001: 9; Number

of LTOs in 2001: 12,355; Oldest in fleet: 1993; Newest

in fleet: 1998; Average

number

of seats: 126.9; Pounds takeoff

weight: 122000.



Model: 737-400; Engine: CFM56-3B-2; Pounds

NOx per LTO[A]: 12.496; Pounds CO

per LTO[A]: 17.811; Pounds VOC

per LTO[A]: 0.991; Number

in U.S. fleet in 2001: 56; Number

of LTOs in 2001: 97,791; Oldest in fleet: 1988; Newest

in fleet: 1992; Average

number

of seats: 144.9; Pounds takeoff

weight: 122000.



Model: 737-400; Engine: CFM56-3C-1; Pounds

NOx per LTO[A]: 14.350; Pounds CO

per LTO[A]: 16.771; Pounds VOC

per LTO[A]: 0.861; Number

in U.S. fleet in 2001: 41; Number

of LTOs in 2001: 71,175; Oldest in fleet: 1989; Newest

in fleet: 1999; Average

number

of seats: 138.9; Pounds takeoff

weight: 133000.



Model: 737-500; Engine: CFM56-3B-1; Pounds

NOx per LTO[A]: 11.617; Pounds CO

per LTO[A]: 19.278; Pounds VOC

per LTO[A]: 1.204; Number

in U.S. fleet in 2001: 26; Number

of LTOs in 2001: 77,823; Oldest in fleet: 1990; Newest

in fleet: 1998; Average

number

of seats: 121.3; Pounds takeoff

weight: 122000.



Model: 737-500; Engine: CFM56-3B-2; Pounds

NOx per LTO[A]: 13.578; Pounds CO

per LTO[A]: 17.894; Pounds VOC

per LTO[A]: 0.994; Number

in U.S. fleet in 2001: 3; Number

of LTOs in 2001: 5,188; Oldest in fleet: 1990; Newest

in fleet: 1990; Average

number

of seats: 104.0; Pounds takeoff

weight: 122000.



Model: 737-500; Engine: CFM56-3C-1; Pounds

NOx per LTO[A]: 15.451; Pounds CO

per LTO[A]: 16.852; Pounds VOC

per LTO[A]: 0.862; Number

in U.S. fleet in 2001: 119; Number

of LTOs in 2001: 197,140; Oldest in fleet: 1990; Newest

in fleet: 1998; Average

number

of seats: 106.5; Pounds takeoff

weight: 122000.



Model: Weighted averages[B]; Pounds

NOx per LTO[A]: 12.123; Pounds CO

per LTO[A]: 16.798; Pounds VOC

per LTO[A]: 1.221; Number

in U.S. fleet in 2001: [Empty]; Number

of LTOs in 2001: [Empty]; Oldest in fleet: [Empty]; Newest

in fleet: [Empty]; Average

number

of seats: [Empty]; Pounds takeoff

weight: [Empty].



Model: Total; Engine: [Empty]; Pounds

NOx per LTO[A]: [Empty]; Pounds CO

per LTO[A]: [Empty]; Pounds VOC

per LTO[A]: [Empty]; Number

in U.S. fleet in 2001: 988; Number

of LTOs in 2001: 1,941,342; Oldest in fleet: [Empty]; Newest

in fleet: [Empty]; Average

number

of seats: [Empty]; Pounds takeoff

weight: [Empty].



Model: Percentage of total U.S. commercial fleet; Number

in U.S. fleet in 2001: 12.7%; Number

of LTOs in 2001: 17.6%; Oldest in fleet: [Empty]; Newest

in fleet: [Empty]; Average

number

of seats: [Empty]; Pounds takeoff

weight: [Empty].



[End of table]



Legend

CO=carbon monoxide

LTO= landing/takeoff

NOx=nitrogen oxides

VOC= volatile organic compounds:



Source: GAO.



Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from 

AvSoft. Emissions were calculated using FAAs Emissions and Dispersion 

Modeling System, version 4.01. The following variables were assumed to 

be the same for all aircraft: (1) taxi-time: 15 minutes, (2) auxiliary 

power unit time: 26 minutes, and (3) ceiling height for emissions 

mixing with local air: 3,000 feet. The models default was used for 

takeoff weight.



[A] Pounds of emissions per one landing/takeoff (LTO), which includes 

emissions for takeoff, climb to 3,000 feet, approach, taxi, and 

auxiliary power unit.



[B] The average was computed by weighting the emissions for a specific 

model/engine combination by the number of landings/takeoffs for that 

combination in 2001.



Table 8: Emission Information for Newest Boeing 737s during Landing/

Takeoff:



Model: 737-700; Engine: CFM56-7B-20; Pounds NOx[A] per LTO: 12.702; 

Pounds CO per LTO: 12.178; Pounds VOC per LTO: 1.370; Number in U.S. 

fleet in 2001: 8; Number of LTOS in 2001: 3,176; Oldest in fleet: 1998; 

Newest in fleet: 2001; Average number of seats: 123.9; Pounds takeoff 

weight: 122000.



Model: 737-700; Engine: CFM56-7B-22; Pounds NOx[A] per LTO: 15.078; 

Pounds CO per LTO: 11.269; Pounds VOC per LTO: 1.183; Number in U.S. 

fleet in 2001: 118; Number of LTOS in 2001: 218,184; Oldest in fleet: 

1997; Newest in fleet: 2002; Average number of seats: 136.9; Pounds 

takeoff weight: 122000.



Model: 737-700; Engine: CFM56-7B-24; Pounds NOx[A] per LTO: 16.971; 

Pounds CO per LTO: 11.229; Pounds VOC per LTO: 1.185; Number in U.S. 

fleet in 2001: 55; Number of LTOS in 2001: 72,337; Oldest in fleet: 

1998; Newest in fleet: 2001; Average number of seats: 123.1; Pounds 

takeoff weight: 122000.



Model: 737-700; Engine: CFM56-7B-26; Pounds NOx[A] per LTO: 20.280; 

Pounds CO per LTO: 9.926; Pounds VOC per LTO: 1.001; Number in U.S. 

fleet in 2001: 5; Number of LTOS in 2001: 2,435; Oldest in fleet: 2001; 

Newest in fleet: 2001; Average number of seats: 124.0; Pounds takeoff 

weight: 122000.



Model: 737-800; Engine: CFM56-7B-26; Pounds NOx[A] per LTO: 20.280; 

Pounds CO per LTO: 9.926; Pounds VOC per LTO: 1.001; Number in U.S. 

fleet in 2001: 193; Number of LTOS in 2001: 208,950; Oldest in fleet: 

1998; Newest in fleet: 2002; Average number of seats: 151.5; Pounds 

takeoff weight: 122000.



Model: 737-800; Engine: CFM56-7B-27; Pounds NOx[A] per LTO: 22.181; 

Pounds CO per LTO: 9.663; Pounds VOC per LTO: 0.934; Number in U.S. 

fleet in 2001: 54; Number of LTOS in 2001: 33,181; Oldest in fleet: 

2000; Newest in fleet: 2002; Average number of seats: 157.0; Pounds 

takeoff weight: 122000.



Model: 737-900; Engine: CFM56-7B-26; Pounds NOx[A] per LTO: 20.030; 

Pounds CO per LTO: 11.221; Pounds VOC per LTO: 1.065; Number in U.S. 

fleet in 2001: 16; Number of LTOS in 2001: 8,285; Oldest in fleet: 

2001; Newest in fleet: 2002; Average number of seats: 161.7; Pounds 

takeoff weight: 122000.



Model: Weighted averages[B]; Pounds NOx[A] per LTO: 17.883; Pounds CO 

per LTO: 10.651; Pounds VOC per LTO: 1.097; Number in U.S. fleet in 

2001: [Empty]; Number of LTOS in 2001: [Empty]; Oldest in fleet: 

[Empty]; Newest in fleet: [Empty]; Average number of seats: [Empty]; 

Pounds takeoff weight: [Empty].



Model: Total; Engine: [Empty]; Pounds NOx[A] per LTO: [Empty]; Pounds 

CO per LTO: [Empty]; Pounds VOC per LTO: [Empty]; Number in U.S. fleet 

in 2001: 449; Number of LTOS in 2001: 546,548; Oldest in fleet: 

[Empty]; Newest in fleet: [Empty]; Average number of seats: [Empty]; 

Pounds takeoff weight: [Empty].



Model: Percentage of total U.S. commercial fleet; Pounds VOC per LTO: 

[Empty]; Number in U.S. fleet in 2001: 5.75%; Number of LTOS in 2001: 

4.96%; Oldest in fleet: [Empty]; Newest in fleet: [Empty]; Average 

number of seats: [Empty]; Pounds takeoff weight: [Empty].



[End of table]



Legend

CO=carbon monoxide

LTO=landing/takeoff

NOx=nitrogen oxides

VOC=volatile organic compounds:



Source: GAO.



Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from 

AvSoft. Emissions were calculated using FAAs Emissions and Dispersion 

Modeling System, version 4.01. The following variables were assumed to 

be the same for all aircraft: (1) taxi-time: 15 minutes, (2) auxiliary 

power unit time: 26 minutes, and (3) ceiling height for emissions 

mixing with local air: 3,000 feet. The models default was used for 

takeoff weight.



[A] Pounds of emissions per one landing/takeoff (LTO), which includes 

emissions for takeoff, climb to 3,000 feet, approach, taxi, and 

auxiliary power unit.



Table 9: Additional Information on Comparison of Older and Newest Model 

Boeing 737 Landing/Takeoff Emissions:



Emission: Nitrogen oxides; Average emission per landing/takeoff: Older 

Boeing 737 (pounds): 12.1; Average emission per landing/takeoff: Newest 

Boeing737 (pounds): 17.8; Changes: 47% increase.



Emission: Carbon monoxide; Average emission per landing/takeoff: Older 

Boeing 737 (pounds): 16.8; Average emission per landing/takeoff: Newest 

Boeing737 (pounds): 10.7; Changes: 37% decrease.



Emission: Hydrocarbons; Average emission per landing/takeoff: Older 

Boeing 737 (pounds): 1.2; Average emission per landing/takeoff: Newest 

Boeing737 (pounds): 1.1; Changes: 10% decrease.



[End of table]



Source: GAO.



Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from 

AvSoft. Emissions were calculated using FAAs Emissions and Dispersion 

Modeling System , version 4.01. The following variables were assumed to 

be the same for all aircraft: (1) taxi-time: 15 minutes, (2) auxiliary 

power unit time: 26 minutes, and (3) ceiling height for emissions 

mixing with local air: 3,000 feet. The models default was used for 

takeoff weight.



The U.S. 2001 commercial fleet included 988 older Boeing 737s. They 

accounted for 17.6 percent of this fleets landings and takeoffs and 

13.4 percent of this fleets nitrogen oxides emissions during landing 

and takeoffs. The U.S. 2001 commercial fleet included 449 newer Boeing 

737s. They accounted for 5.0 percent of this fleets landings and 

takeoffs and 5.5 percent of this fleets nitrogen oxides emissions 

during landing and takeoffs. See table 2 also.



Table 10: Additional Information on Comparison of Boeing 747 and 777 

Emissions on a Per Aircraft Basis:



Emission: Nitrogen oxides; Emission per aircraft during landing/

takeoff: Boeing 747-400 (pounds): 103.5; Emission per aircraft during 

landing/takeoff: Boeing B777-200ER (pounds): 124.2; Changes: 20 percent 

increase.



Emission: Carbon monoxide; Emission per aircraft during landing/

takeoff: Boeing 747-400 (pounds): 47.7; Emission per aircraft during 

landing/takeoff: Boeing B777-200ER (pounds): 30.4; Changes: 36 percent 

decrease.



Emission: Hydrocarbons; Emission per aircraft during landing/takeoff: 

Boeing 747-400 (pounds): 4.1; Emission per aircraft during landing/

takeoff: Boeing B777-200ER (pounds): 2.4; Changes: 41 percent decrease.



[End of table]



Source: GAO.



Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from 

AvSoft. Emissions were calculated using FAAs Emissions and Dispersion 

Modeling System, version 4.01. The following variables were assumed to 

be the same for all aircraft: (1) taxi-time: 15 minutes, (2) auxiliary 

power unit time: 26 minutes, and (3) ceiling height for emissions 

mixing with local air: 3,000 feet. The models default was used for 

takeoff weight. See table 3 also.



The Boeing B77-200ER data is the weighted average (based on 2001 

landings and takeoffs) for three different engines. The nitrogen oxides 

and other emission characteristics of these engines vary significantly.



The 58 Boeing 747-400s in the 2001 U.S. fleet have PW4056 engines and 

average 361 seats per aircraft. The 101 Boeing 777-200ERs in the 2001 

U.S. fleet have the following engines: PW4090 

(37 aircraft averaging 302 seats), GE90-90B (16 aircraft averaging 283 

seats), and TRENT 892B-17 (48 aircraft averaging 249 seats). The three 

engine types for the Boeing 777-200ERs emit 138.6, 123.6, and 112.3 

pounds of nitrogen oxide emissions per landing/takeoff, respectively.



Table 11: Comparison of Power, Engine Operating Pressures, and Nitrogen 

Oxides Emissions for a Boeing 737-300 and Its Most Common Replacement:



Engine variant; Older model: B737-300: CFM56 3B-1; Newer model: B737-

700: CFM56 7B-22.



Power (thrust) per engine; Older model: B737-300: 89 kiloNewtons; 

Newer model: B737-700: 101 kiloNewtons.



Engine operating pressure ratio; Older model: B737-300: 22.4; Newer 

model: B737-700: 24.41.



Landing/takeoff nitrogen oxides emissions; Older model: B737-300: 

10.72 pounds; Newer model: B737-700: 15.08 pounds.



[End of table]



Source: GAO.



Notes: Aircraft engine emissions data obtained from ICAO. Calculations 

made using FAAs Emissions and Dispersion Modeling System, version 

4.01. Landing/takeoff emission computations assume typical conditions 

of 3,000 foot mixing height, 15-minute taxi, and 26 minute auxiliary 

power unit usage and 122,000 pound takeoff weight. See table 5 also.



Other details: B737-300 B737-700

Takeoff weight used for comparison: 122,000 lbs. 22,000 lbs.

Average seat count: 131 137

Number in 2001 commercial fleet: 380 118

Production years for U.S. fleet: 1984-1997 1997-present

Percent of 2001 commercial fleet landings/takeoffs: 7.7% 2.0%

Other landing/takeoff emissions in pounds:

 Carbon monoxide improved 41%: 19.20 lbs. 11.27 lbs.

 Hydrocarbons improved 1.5%: 01.20 lbs. 01.18 lbs.



[End of section]



Appendix VIII: Comments from the National Aeronautics and Space 

Administration:



National Aeronautics and Space Administration:



Office of the Administrator Washington, DC 20546-0001:



February 27, 2003:



Gerald L. Dillingham, PhD. Director, Civil Aviation Issues U S. General 

Accounting Office 441 G. St. N. W.

Room 2T23 Washington, DC 20548:



Dear Dr. Dillingharn.:



Thank you for giving us the opportunity to review and comment on (GAO) 

Draft Report: Aviation and the Environment: Strategic Framework Needed 

to Address Challenges Posed by Aircraft Emissions.



We concur with the reports conclusion that the Environmental Protect-

ion Agency and the National Aeronautics and Space Administration (NASA) 

should work together under the Federal Aviation Administrations 

leadership to develop a strategic framework for addressing emissions 

from aviation-related sources.



Comments on the reports content relative to NASA programs are provided 

in the enclosure. If we can be of further assistance, please do not 

hesitate to call Terrence Hertz at 358-4636.



Signed by Frederick D. Gregory:



Frederick D. Gregory Deputy Administrator:



Enclosure:



[End of section]



Appendix IX: GAO Contacts and Staff Acknowledgments:



GAO Contacts:



Gerald L. Dillingham (202) 512-3650

Teresa Spisak (202) 512-3950:



Staff Acknowledgments:



In addition to the individuals named above, Carolyn Boyce, Joyce Evans, 

David Hooper, David Ireland, Art James, Jennifer Kim, Eileen Larence, 

Edward Laughlin, Donna Leiss, Jena Sinkfield, Larry Thomas, and 

Gail Traynham made key contributions to this report.



FOOTNOTES



[1] U. S. General Accounting Office, Aviation and the Environment: 

Airport Operations and Future Growth Present Environmental Challenges, 

GAO/RCED-00-153 (Washington, D.C.: Aug. 30, 2000).



[2] Energy and Environmental Analysis, Inc. for Industrial Economics 

submitted to EPA Analysis of Techniques to Reduce Air Emissions at 

Airports (Draft Final Report) (Washington, D.C.: June 1997).



[3] Federal Aviation Administration, FAA Long-Range Aerospace Forecasts 

Fiscal Years 2015, 2020 and 2025, FAA-APO-01-3 (Washington, D.C.: June 

2001).



[4] ICF Consulting Group, Evaluation of Air Pollutant Emissions from 

Subsonic Commercial Jet Aircraft, EPA420-R-99-013 (Washington, D.C.: 

April 1999). In this report, which was prepared for EPA, the agency 

acknowledged that some groups, including the air transport industry 

were critical of the growth projections, fleet turnover assumptions, 

and emissions estimates used in the report. As a result, these groups 

believe the report overstates the amount of emissions generated by 

aircraft. 



[5] Department of Transportation, Office of the Inspector General, 

Airline Industry Metrics (Washington, D.C.: January 7, 2003).



[6] 42 U.S.C. 7401-7626. 



[7] State implementation plans are based on analyses of emissions from 

all sources in the area and computer models to determine whether air 

quality violations will occur. If data show that air quality standards 

will be exceeded, the states are required to impose controls on 

existing emission sources to prevent this situation.



[8] The criteria pollutants are carbon monoxide, lead, nitrogen 

dioxide, particulate matter, ozone, and sulfur dioxide.



[9] 49 U.S.C. section 47106.



[10] Major commercial airports are the 50 busiest airports in 2001, 

based on air carrier operations at those airports.



[11] The reduction was calculated using total nitrogen oxide emissions 

from John L. Kennedy International and LaGuardia Airports for 1999.



[12] 49 U.S.C. section 47136.



[13] The 10 airports are Atlanta Hartsfield, Baltimore Washington 

International, Baton Rouge Metropolitan, Denver International, Dallas/

Fort Worth International, New York John F. Kennedy International, New 

York LaGuardia, Chicago OHare International, San Francisco 

International, and Sacramento International. 



[14] FAAs Airport Improvement Program provides grants to airports for 

capital development. FAA allocates most grants on the basis of a 

legislated formula tied to the number of passengers an airport enplanes 

and categories earmarked for specific types of airports and projects.



[15] Most airports are able to charge passengers a boarding fee, called 

a passenger facility charge, to help pay for their capital development 

projects. The program is managed by FAA, which approves an airports 

application to participate and the specific projects to be funded.



[16] For example, if an airport produces 100 tons of nitrogen oxides 

per year and then voluntarily initiates a project that reduces the 

amount by 10 tons, the baseline becomes 

90 tons. If an expansion project then results in a 10-ton yearly 

increase in nitrogen oxides, the airport might have to initiate new 

mitigation measures that will compensate for the increase.



[17] In September 2002, FAA and EPA issued guidance for airports 

developing early emissions reduction programs.



[18] The 13 states encompass all 26 of the top 50 busiest commercial 

airports located in areas designated as not in attainment for ozone.



[19] Market-based options are rewards or inducements to reduce 

emissions. They can be in the form of charges, emission credit-trading 

regimes, and voluntary measures. According to ICAO, market-based 

measures are policy tools that are designed to achieve environmental 

goals at a lower cost and in a more flexible manner than traditional 

emission reduction measures.



[20] Emissions trading is a market based approach to reducing 

emissions. As practiced in the United States, a cap or limit is set 

on the amount of emissions allowed from regulated sources, such as 

power plants. The cap is set lower than historical emissions to cause 

reductions. Sources are then given an allowance, which authorizes them 

to emit a fixed amount of a pollutant. Sources whose emissions are 

lower than their allowance, can sell the remainder of their allowance 

on the open market to sources that have exceeded their allowance. 



[21] Massachusetts Port Authority, Air Quality Initiative for Boston 

Logan International Airport (March 2001).



[22] To the extent possible, we compared aircraft that can be used 

interchangeably to fulfill the same mission (same number of passengers, 

same range). In instances where aircraft fly the same routes but have 

different seating capacity, we made comparisons on a per seat basis. 

The most straightforward comparison of newest versus older aircraft 

emissions involves the various Boeing 737 models. This family of 

medium-sized jets made 

22.6 percent of all landings and takeoffs in the 2001 U.S. aircraft 

fleet. Furthermore, all models in this family have been updated in the 

last 5 years with improved airframes and engines.



[23] The U.S. 2001 commercial fleet included 988 older Boeing 737s. 

They accounted for 

17.6 percent of this fleets landings and takeoffs and 13.4 percent of 

this fleets nitrogen oxides emissions during landing and takeoffs. The 

U.S. 2001 commercial fleet included 

449 newer Boeing 737s. They accounted for 5.0 percent of this fleets 

landings and takeoffs and 5.5 percent of this fleets nitrogen oxide 

emissions during landings and takeoffs.



[24] Almost all that is known about the emission characteristics of a 

particular engine comes from these certification tests, which cover 

four modes of the landing/takeoff cycle (taxi in/taxi out, takeoff, 

climb out, and approach). Landing/takeoff emissions are derived from 

computer models that combine the engine certification emission data 

with characteristics of specific aircraft.



[25] The ICAO Engine Exhaust Emissions Data Bank lists the power of the 

CFM56 3B-1 engine (used on the Boeing 737-700) at 89.4 kiloNewtons. The 

CFM56 7B-20 (used on the Boeing 737-700) is rated at 91.6 kiloNewtons.



[26] According to FAA, this approach has produced an aircraft fleet 

that is about 65 percent more fuel efficient than in 1970 and aircraft 

engines with a high safety record.



[27] The new fuel-efficient engines are operating at increasingly 

higher engine operating pressures. The nitrogen oxides emissions 

standards allow for increasing emissions as this pressure increases.



[28] National Research Council, For Greener Skies, Reducing 

Environmental Impacts of Aviation (Washington, D.C.: National Academy 

Press, 2002).



[29] According to FAA official, aircraft are more heavily regulated 

than other mobile sources in terms of design, maintenance, and 

operation and have safety and noise regulations that other mobile 

sources lack.



[30] National Research Council, For Greener Skies, Reducing 

Environmental Impacts of Aviation (Washington, D.C.: National Academy 

Press, 2002).



[31] Ibid.



[32] Howard G. Aylesworth, Jr. and Peter Newton, Qualitative Standards 

of the Environmental Effectiveness of International Civil Aviation 

Organization Emissions Standards and Recommended Practices, Handbook 

of Airline Strategy: Public Policy, Regulatory Issues, Challenges, and 

Solutions (Washington, D.C: Aviation Week, 2001).



[33] ICAOs analyses use 26 minutes as the default value for taxi-time. 

Our analysis of information provided by FAA indicated that 15 minutes 

was a more appropriate value for the large number of U.S. airports in 

our analysis.



[34] Environmental Protection Agency, National Air Quality and 

Emissions Trends Report, 1999, EPA 454/R-01-004 (Washington, D.C.: 

March 2001).



[35] ICF Consulting Group, Evaluation of Air Pollutant Emissions from 

Subsonic Commercial Jet Aircraft, EPA420-R-99-013 (Washington, D.C.: 

April 1999). In this report, which was prepared for EPA, the agency 

acknowledged that some groups, including the air transport industry 

were critical of the growth projections, fleet turnover assumptions, 

and emissions estimates used in the report. As a result, these groups 

believe the report overstates the amount of emissions generated by 

aircraft.



[36] Dallas/Fort Worth International Airport, Inventory of Air 

Emissions (July 1998).



[37] The City of Chicago, Findings Regarding Aircraft Emissions: OHare 

Airport and Surrounding Communities (December 1999).



[38] Massachusetts Port Authority, Air Quality Initiative for Boston 

Logan International Airport (March 2001).



[39] Our estimates were developed from information contained in Dallas/

Fort Worth International Airport Emissions Inventory (July 1998) and 

emissions inventories for the Dallas/Forth Worth metropolitan area 

contained in that areas State Implementation Plan.



[40] Energy and Environmental Analysis, Inc., Analysis of Techniques to 

Reduce Air Emissions at Airports, (Arlington, VA: June 1997). The four 

airports included in this study, which was conducted for EPA, were 

Baltimore-Washington International Airport, Boston Logan International 

Airport, Los Angeles International Airport, and Phoenix Sky Harbor 

International Airport.



[41] According to EPA, mobile sources are moving objects that release 

pollution; mobile sources include cars, trucks, buses, planes, trains, 

motorcycles, and gasoline-powered lawn mowers. Mobile sources are 

divided into two groups: road vehicles, which include cars, trucks and 

buses, and nonroad vehicles, which include trains, planes, and lawn 

mowers. Mobile sources are distinguished from stationary sources, which 

are places or objects from which pollutants are released and which do 

not move around. Stationary sources include power plants, gas stations, 

incinerators, houses, etc.



[42] Environmental Protection Agency, Environmental Fact Sheet: Adopted 

Aircraft Emissions Standards (EPA 420-F-97-010, April 1997) and Federal 

Aviation Administration, Air Quality Procedures For Civilian Airports 

and Air Force Bases (Washington: April 1997).



[43] Intergovernmental Panel on Climate Change, Aviation and the Global 

Atmosphere (1999).



[44] 42 U.S.C 7401-7626. The amendment to the Clean Air Act in 1990 

provided for a number of related programs designed to protect health 

and control air pollution. The 1990 amendments established new programs 

and made major changes in the ways that air pollution is controlled. 

See U.S. General Accounting Office, Air Pollution: Status of 

Implementation and Issues of the Clean Air Act Amendments of 1990, GAO/

RCED-00-72 (Washington, D.C.: Apr.17, 2000).



[45] See 42 U.S.C. 7571 of the Clean Air Act.



[46] California is authorized, under section 209(e)(2)(B) of the Clean 

Air Act to enact and enforce nonroad engine standards, which apply to 

ground support equipment. States with nonattainment areas can 

promulgate standards identical to those of California. Otherwise, the 

federal standard applies. In November 2002, EPA adopted emissions 

standards for nonroad large spark emissions engines such as those used 

in much of the ground support equipment currently in service at 

airports.



[47] The airports in the Los Angeles region include Burbank, Long 

Beach, Los Angeles International, John Wayne (Orange County), Ontario 

International, and Palm Springs International.



[48] The California Air Resources Board has reached agreement with the 

major carriers in Southern California to reduce emissions from ground 

support equipment.



[49] 49 U.S.C. 47106.



[50] The 1-hour ozone standard is the average amount of ozone allowed 

by EPA in the lower atmosphere during a one-hour period. 



[51] The agencys name was recently changed to the Texas Commission on 

Environmental Quality.



[52] Air carrier representatives have noted that the airports proposed 

strategies could be subject to legal challenge if they are implemented.



[53] Federal Aviation Administration, Air Quality Procedures For 

Civilian Airports and Air Force Bases (Washington, D.C.: April 1997).



[54] Federal Aviation Administration, Air Quality Procedures For 

Civilian Airports and Air Force Bases (Washington: April 1997).



[55] NASA officials told us that their nitrogen oxide research goals 

are more ambitious than what they expect to actually achieve when their 

research is incorporated into production ready engine designs. This is 

because designs that work well during component level research testing 

will undergo modification as the complete engine design is refined to 

meet safety and operability requirements and fuel-efficiency goals.



[56] FAA, the aviation industry, and universities also participate with 

this research. 



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