Office of Environment and Energy January 2015

Aviation Emissions, Impacts & Mitigation: A Primer

Aviation Emissions, Impacts & Mitigation

A Primer

FAA Office of Environment and Energy

January 2015
Aviation & Emissions – A Primer

Table of Contents

Introduction ................................................................................... 1

Aviation Emissions........................................................................ 2

Emission Impacts ........................................................................ 10

Mitigating Aviation Emissions .................................................. 22

Conclusion................................................................................... 31

Abbreviations & Acronyms ........................................................ 33

End Notes .................................................................................... 35
Aviation and the Environment: A Primer

Introduction

Transportation is an essential contributor to the health and well-being of the nation’s economy. Within the 

transportation sector, commercial aviation has evolved into the fastest, safest, and most far-reaching 

transportation mode in little more than a century. The world economy benefits greatly from the ability to 

move people and products all over the globe - quickly and safely. The statistics are impressive. Today, 

over 3 billion people, nearly half the global population, use the world’s airlines.

1 The air transport industry 

provides 56 million direct, indirect, and induced jobs worldwide, which is double the number of jobs only 

eight years ago. While aircraft carry only 0.5% of world trade shipments, that represents about 35% of the 

value of all world trade.

2 This productivity is achieved consuming just 2.2% of world energy. 3

Aviation contributes to quality of life – allowing us to visit friends and relatives, to travel, to experience 

new places, to shrink the world. Aviation must develop if it is to continue to meet the needs of a growing 

economy and an expanding population. At the same time, aviation must be environmentally sustainable, 

operating harmoniously within the constraints imposed by the need for clean air and water, limited noise 

impacts, and a livable climate.

The Federal Aviation Administration (FAA) is working with other stakeholders to transform the aviation 

system to address the challenges and opportunities of the future. In July 2012, it published the “Aviation 

Environmental and Energy Policy Statement”4 which identifies and reaffirms FAA’s commitment to 

environmental protection that allows sustained aviation growth. The Policy Statement lists the guiding 

principles of: 1) limiting and reducing future aviation environmental impacts to levels that protect public 

health and welfare and 2) ensuring energy availability and sustainability.

FAA’s Next Generation Air Transportation System (NextGen) will establish the programs, systems, and 

policies needed for safer, responsive, and more efficient air transport. The FAA’s Office of Environment 

and Energy (AEE) is working to develop new technologies, operations, systems, and fuels to ensure 

aviation can meet the goals of NextGen while minimizing aviation’s impact on the environment. AEE has 

established a strategic framework to guide research programs for mitigating the environmental impacts of 

aviation. The framework calls for working with the Environmental Protection Agency (EPA), the National 

Aeronautics and Space Administration (NASA), and other federal agencies as well as industry stakeholders 

and academia to ensure aviation emissions do not pose health concerns for U.S. citizens or degrade the 

global climate.

Aviation affects the environment in many ways: people living near airports are exposed to noise from 

aircraft; streams, rivers, and wetlands may be exposed to pollutants discharged in storm water runoff from 

airports; and aircraft engines emit pollutants to the atmosphere. This primer describes the emissions 

associated with commercial aviation and the health and welfare impacts that can result from those aviation 

emissions that degrade not only air quality but also the broader climate. Noise5 and water quality6

considerations are not included in this report but are addressed in other FAA materials. 

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Aviation Emissions, Impacts & Mitigation: A Primer

Aviation Emissions

Aircraft, cars, trucks, and other vehicles operating at the airport create emissions as a result of the 

combustion of fuel as summarized in Table 1. Aircraft engines produce carbon dioxide (CO2), which 

comprises about 70% of the exhaust, and water vapor (H2O), which comprises about 30%. Less than 1% of 

the exhaust is composed of pollutants like nitrogen oxides (NOx), oxides of sulfur (SOx), carbon monoxide 

(CO), partially combusted or unburned hydrocarbons (HC), particulate matter (PM), and other trace 

compounds.

Generally, about 10 percent of aircraft pollutant emissions7 are emitted close to the surface of the earth (less 

than 3000 feet above ground level). The remaining 90 percent of aircraft emissions are emitted at altitudes 

above 3000 feet. The pollutants CO and HCs are exceptions to this rule as they are produced when aircraft 

engines are operating at their lowest combustion efficiency (while wheels are on the ground), which makes

their split about 30 percent below 3000 feet, and 70 percent above 3000 feet.

8

Aircraft are not the only source of aviation emissions. Airport access and ground support vehicles typically 

burn fossil fuels and produce similar emissions. This includes traffic to and from the airport, shuttle buses 

and vans serving passengers, and ground support equipment (GSE) that services aircraft. Other common 

emissions sources at the airport include auxiliary power units (APU) providing electricity and air 

conditioning to aircraft parked at airport terminal gates, stationary airport power sources, and construction 

equipment operating on the airport.

Emission Formation and Transformation.

Many of the pollutants that form in the combustion process transform when they are emitted to the 

atmosphere. Aircraft pollutants generally transform in three different zones: 1) immediately after exiting 

the combustor within the engine, 2) downstream from the engine in the hot exhaust plume, and 3) after 

emissions have cooled and mixed with the ambient atmosphere. At the aircraft engine exit, hot combustion 

gases mix with ambient air to quickly cool the gas stream. Some gases, like heavy hydrocarbons, can 

condense under these conditions to form aerosol particles. In the exhaust plume, as emissions continue to 

cool, some molecules undergo chemical reactions producing other molecules that can also condense into 

particles. Small particles in the plume collide and form larger particles, although still microscopic in size.

The resulting PM in the plume can be solid or liquid and include carbon in the form of soot, inorganic salts 

(like ammonium nitrate and ammonium sulfate), and heavy hydrocarbons that condense into aerosol 

particles.

Likewise, gaseous and particle emissions from cars, trucks, and ground vehicles that have exhaust pipes, 

catalytic converters or particle traps, and mufflers, transform in the exhaust plume after mixing with the 

ambient atmosphere. Most of the aviation-related PM that reaches airport communities are particle 

emissions that are released during ground operations and landing and takeoff. Local communities are less 

affected by PM emissions from cruise operations.

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Aviation Emissions, Impacts & Mitigation: A Primer

Table 1: Aviation Emissions

Emission Description Emission Sources Impacts

CO2 Carbon dioxide is the product of complete 

combustion of hydrocarbon fuels like 

gasoline, jet fuel, and diesel. Carbon in 

fuel combines with oxygen in the air to 

produce CO2

• Aircraft

• APU

• GSE

• Vehicles

• Stationary power plants

• Construction equipment

• Climate change

H2O Water vapor is the other product of 

complete combustion as hydrogen in the 

fuel combines with oxygen in the air to 

produce H2O. This is the source of water 

in condensation trails (contrails).

• Aircraft 

• APU

• GSE 

• Vehicles 

• Stationary power plants

• Construction equipment

• Climate change 

NOx Nitrogen oxides are produced when air 

passes through high temperature/high 

pressure combustion and nitrogen and 

oxygen present in the air combine to form 

NOx. Contributes to ozone and secondary 

particulate matter formation.

• Aircraft 

• APU

• GSE 

• Vehicles 

• Stationary power plants

• Construction equipment

• Air quality

• Climate change

HC Hydrocarbons are emitted due to 

incomplete fuel combustion. They are 

often referred to as unburned 

hydrocarbons (UHC) or volatile organic 

compounds (VOCs) [VOC excludes some 

low reactivity compounds found in 

measures of HC9

] Some of the 

compounds in the HC emissions are toxic 

and hazardous air pollutants (HAPs).

Contributes to ozone formation.

• Aircraft 

• APU

• GSE 

• Vehicles 

• Stationary power plants

• Construction equipment

• Air quality

CH4 Methane is the most basic hydrocarbon. 

Commercial aircraft are net consumers of 

methane during cruise and are not listed 

in the emissions source column. The net 

impact of methane from airport sources is

highly dependent on local circumstances.

• APU

• GSE 

• Vehicles 

• Stationary power plants

• Construction equipment

• Air quality

CO Carbon monoxide is formed due to the 

incomplete combustion of the carbon in 

the fuel. Contributes to ozone formation.

• Aircraft

• GSE 

• Vehicles 

• Construction equipment 

• Air quality

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Aviation Emissions, Impacts & Mitigation: A Primer

SOx Sulfur oxides are produced when small 

quantities of sulfur, present in essentially 

all petroleum fuels, combine with oxygen 

from the air during combustion. 

Contributes to secondary particulate

matter formation.

• Aircraft 

• APU

• GSE

• Construction equipment 

• Air quality

• Climate change 

Particulate 

Matter 

(non-volatile)

Small particles of soot (a.k.a. black 

carbon) that form as a result of 

incomplete combustion and aerosols from 

condensed gases, which are small enough 

to be inhaled, are referred to as particulate 

matter. Discussed in detail in Health and 

Environmental Effects Section.

• Aircraft 

• APU

• GSE 

• Vehicles 

• Stationary power plants

• Construction equipment 

• Air quality

• Climate change

As aircraft and vehicle emissions mix with the ambient atmosphere, further chemical reactions occur. 

These reactions involve both molecules emitted from the aircraft and vehicle engines as well as molecules

already in the air. For example, ozone is formed by the reaction of VOCs and NOx in the presence of heat 

and sunlight. Also, complex chemical reactions and/or particle nucleation processes can produce new 

particles or add to pre-existing particles. The subsequent particles that are formed can be an order of 

magnitude greater than primary particles10. These particles are estimated to represent more than 95% of 

total particle formation11 and expose people over a much broader geographic range. Other examples are the 

conversion of nitrogen dioxide (NO2) from the plume to nitric acid (HNO3) vapor that interacts with 

ammonia in the atmosphere and forms ammonium nitrate (NH4NO3) particles and oxidation reactions 

involving gaseous hydrocarbons from the plume, yielding condensable organic compounds that form 

organic aerosol particles. Ammonia, stemming primarily from agricultural activities, is the main alkaline 

component in the atmosphere and is highly reactive in forming aerosols.

Aviation Climate Change Emissions Compared to Other Transportation Modes.

Only some, but not all, greenhouse gas emissions, such as CO2, are directly related to fuel use, and most 

transportation modes use similar fuels. For that reason, energy intensity – the amount of energy consumed 

to transport one passenger one mile – is a useful metric for comparing greenhouse gas emissions among 

different transportation modes. Rail, at 2,750 BTU/passenger miles, has the lowest energy use per 

passenger mile among primary transport modes and transit buses the highest at 4,364 BTU/passenger 

miles.

12 Aviation and automobiles have efficiencies between those two.

Aviation stands out among transportation modes, however, in terms of improving fuel efficiency over the 

past decade. As shown in Figure 1: Comparison of Vehicle Fuel Efficiency, in 2004, automobiles and 

airlines operating in the U.S. had very similar energy intensities, with automobiles at 3,496 BTU/passenger 

mile versus airlines at 3,505 BTU/passenger mile. Between 2004 and 2012, auto energy intensity fell to 

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Aviation Emissions, Impacts & Mitigation: A Primer

3,193 BTU/passenger mile, for an 8.8% improvement. For the same period, aviation energy intensity fell 

to 2,654 BTU/passenger mile, a 24.3% improvement and is now significantly lower than automobiles.

These trends were confirmed in a recent study. Aviation is now approaching rail as the most energy 

efficient transportation mode based on energy intensity per passenger mile. 

Figure 1: Comparison of Vehicle Fuel Efficiency

U.S. data for different transportation modes from various government agency data resources as 

compiled by the Oak Ridge National Laboratory Center for Transportation Analysis13

Aviation Emissions Compared to Other Transportation Modes. 

Aviation has grown faster than other modes of transportation and is expected to outpace them in the future. 

Despite this growth, aviation’s contribution to emissions inventories compared to other transportation 

sources has remained modest, particularly compared to on-road sources. Although the rate of growth in the 

mass of aviation NOx emissions has exceeded on-road (i.e., cars and trucks) NOx emissions growth, the 

quantity of emissions of other transport modes still far exceeds those from aviation as illustrated in Figure 

2: Transportation Emissions. In part this is not surprising as most of an aircraft’s operations take place at 

altitude where emissions have an uncertain and indirect effect on ground-level air quality spread out over a 

wide geographic area. This is in contrast to cars and trucks that primarily operate within a single air quality 

region and always at ground level. 

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Aviation Emissions, Impacts & Mitigation: A Primer

Figure 2: U.S. Transportation Emissions

2011 total U.S. pollutant emissions from primary transportation modes14

In the future, NOx emissions from on-road vehicles will fall in response to the most recent environmental 

regulations, which call for nearly doubling corporate average fuel economy from 29 miles per gallon 

currently to 54.5 miles per gallon by 2025.

15 Nonetheless, pressure on aviation sources will likely remain 

as many states and localities will face the challenges of meeting new ozone and particulate matter standards 

at the same time non-aviation source reductions become more difficult and costly. 

Aviation Emissions Compared to Other Sources of Emissions. 

There is an understandable interest in comparing the total mass of emissions coming from an airport to 

those of a power plant or petroleum refinery in the same region.

16 Airports, however, are quite different 

from most other emissions sources. Like cities, they comprise a variety of different emission sources. 

Aircraft arrive at the airport, stay for a short period and depart, with a different aircraft taking off or landing 

every few minutes. Passenger cars, shuttle buses, and taxis calling on the airport do not operate there 

exclusively, also serving homes and retail, commercial, and governmental establishments. Power boilers 

and chillers at the airport are independently permitted, as is similar equipment at other locations. For these 

reasons it is difficult to compare the composite of sources that make up an airport to another emission 

source like an industrial facility or power plant. Table 2 provides a list of the contributions of aircraft 

emissions to major metropolitan statistical areas inventories with the highest contribution of aircraft 

emissions to total inventory.

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Aviation Emissions, Impacts & Mitigation: A Primer

Table 2: Aircraft Emissions Contribution to Metropolitan Area Emissions Inventories 

Metropolitan Area NOx% VOC% PM2.5%

Washington, DC 1.22 0.57 0.21

Philadelphia 0.64 0.35 0.20

New York 1.40 0.42 0.41

Denver 1.42 0.54 0.31

San Francisco 1.57 0.63 0.29

Dallas 1.76 0.58 0.23

Minneapolis 1.07 0.59 0.39

Chicago 1.27 0.49 0.36

The contribution of aircraft LTO (Landing-Take Off) operations at commercial service airports to 

emissions inventories has been calculated at an average of 0.37% for SOx (with a range of 0.002% to 

6.91%) and 0.44% for CO (ranging from 0.06% to 4.36%).17

Effects of Economic Growth on Emissions.

The level of aviation activity reflects the overall demand for worldwide travel and trade. Demand for travel 

services, both passenger travel and freight transportation, increased substantially in the last third of a 

century. Since 1980, gross domestic product (GDP) in the U.S. has increased by 140%18 and air travel has 

increased by 134%.19 Over the long term, it is expected that demand for air transportation will continue to 

grow. Current forecasts are for 2.3% per year growth of enplanements over the next two decades, resulting 

in 58% more passengers.20 As a result, growth of the aircraft fleet and expansion and further development 

of existing airports are expected. This also means that emissions from aviation activity are expected to 

increase unless the improvements in operational efficiency, sustainable alternative fuels, and associated 

low-emissions technologies discussed below can offset that growth. 

Trends in Aviation Emissions.

While aviation activity is forecasted to grow, emissions are also dependent on other factors including:

• Aircraft construction materials and technological sophistication – the lighter, more 

aerodynamic and technologically sophisticated an aircraft is, the less fuel it will use. 

• Aircraft operations – the less time an aircraft spends taxiing or idling on the ground and the 

more direct routing a flight can take, the less fuel it will use. Restricted or congested air space, 

adverse weather, congested airports, and inefficient ground operations can all result in 

increased emissions.

• Fuel composition – while they are needed in small quantities, the presence of sulfur and heavy 

or complex hydrocarbon molecules such as aromatic compounds create particle pollutants and 

reduce combustion efficiency. 

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Aviation Emissions, Impacts & Mitigation: A Primer

As demonstrated by the fuel efficiency trends in Figure 1, technological advancement in aircraft engine 

design has reduced aircraft fuel consumption and emissions on a per flight basis significantly over the past 

several decades. During this same era, the industry developed and deployed new, lightweight, highstrength materials, automated navigational, operational, and engine control systems, and employed vast 

new computational capabilities to improve aerodynamic efficiency and integrate highly complex 

operational structures such as hub and spoke airport networks. Jet aircraft in service today are over 70% 

more fuel efficient per seat-kilometer than the first jets in the 1960s.21

Although new aircraft are significantly more fuel efficient, average fuel economy for the worldwide 

commercial aircraft fleet improves slowly because commercial passenger service aircraft typically remain 

in the fleet for 30-35 years. As they age, existing aircraft are retired and replaced with new aircraft as 

illustrated in Figure 3: Growth and Replacement of Passenger Aircraft. New aircraft also are added to the 

fleet for new capacity. In 10 years, 52% of the fleet will be new aircraft, increasing to 86% in 20 years. 

These new aircraft will incorporate advanced technology and capabilities with a corresponding 

improvement in fuel efficiency. 

Figure 3: Growth and Replacement of Passenger Aircraft

Worldwide fleet growth and replacement forecast based on historic aircraft retirement for large 

commercial aircraft 22

The FAA today is focused on transforming the Nation’s airspace system. The Agency has launched the 

NextGen program,

23 which will overhaul the nation’s air traffic control system. Significant effort is going 

into reducing congestion and delay. The planned improvements will also increase system reliability. These 

changes will speed up the reductions in emissions on a per flight basis.

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Aviation Emissions, Impacts & Mitigation: A Primer

Efforts are underway to improve the jet fuel being used, which has the effect of reducing emissions. New 

alternative fuels such as those produced from biological materials could dramatically reduce aviation CO2

emissions. By tailoring fuel quality to engine design aircraft will be able to produce fewer emissions per 

flight. Jet fuel issues are the subject of research by the Partnership for Air Transportation Noise and 

Emissions Reduction (PARTNER) program. Recently completed Project 28 (Environmental Cost-Benefit 

Analysis of Alternative Jet Fuels)24 has significantly improved understanding of the environmental costs 

and benefits of alternative jet fuels. It evaluated life cycle greenhouse gas emissions from alternative jet 

fuels on a screening level, developed a first-order fuel production cost model, developed alternative fuel 

usage scenarios that deliver specified greenhouse gas reductions and expanded the environmental analysis 

to consider sustainability in terms of land, water, and air. The sustainability assessment started under 

Project 28 is the primary basis for ongoing research extending the applicability of that assessment to 

additional technology sets and feedstock options, to develop scenarios for biofuel deployment, and to 

conduct tradeoff analyses among different metrics and options. Alternative jet fuel sustainability has 

become a focused topic for research by the FAA. The results of this work are relevant to the NextGen

environmental and energy goals relating to the development of alternative jet fuels, and offer important 

information to regulators, fuel producers and fuel procuring agencies as to the overall sustainability of 

different feedstock and technology options.

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Aviation Emissions, Impacts & Mitigation: A Primer

Emission Impacts

Aviation emissions affect both air quality and the global climate. Compared to other economic sectors, 

commercial aviation is a relatively small contributor to emissions of concern for both air quality and 

climate change. However, aviation emissions occur in the climatically sensitive upper troposphere and 

lower stratosphere where they may have a disproportionate impact on climate. They also occur at high 

altitudes where their impact may be felt at large distances away from where they are released. 

In this section we discuss how aircraft emissions affect human health and the environment and how they 

are regulated to limit harmful effects. There are three factors to consider in evaluating emissions’ impacts: 

1) The quantity and characteristics of emissions; 2) how humans and sensitive environments get exposed to 

them; and 3) their human health and environmental effects. 

Measuring Aviation Emissions.

Aviation stakeholders, including the FAA, commercial airlines, airframe and engine manufacturers, NASA, 

EPA, and the U.S. military, have a long history of conducting research to measure the amount and 

composition of aviation emissions. In recent years there have been several emission measurement 

programs that have significantly increased the knowledge of aircraft emissions. The Aircraft Particle 

Emissions eXperiment (APEX)25 tests were conducted between 2004 and 2006 and measured emissions 

throughout the power range of aircraft engines using a variety of fuels. The tests measured emissions at the 

exit of the engine as well as downstream in the exhaust plume as they cooled and mixed with ambient air to 

evaluate the chemical and physical changes that take place. Engines of various sizes were included in these 

programs. More recent tests have measured emissions from other aviation sources such as APU, GSE, and 

aircraft tires and brakes.

Knowing the amount and characteristics of the emissions from various aviation sources is only part of the 

story. It is also important to know about their combined emissions at airports. The FAA,

26 commercial 

airports, the U.S. military,

27 National Academy of Science Transportation Research Board,28 and other 

stakeholders have carried out several projects that measured emissions and air quality in and around 

airports. Measurements have been conducted on airports, in communities adjacent to airports, and 

downwind of airports for airports ranging from large hub airports to small, local airports. 

Over the past decade many more projects29 have measured and characterized aviation emissions. These 

projects have helped researchers understand where emissions are released, what they are made of and how

they change chemically and physically, how they disperse in the air, and where they end up.

Today a great deal is understood about the amount and type of emissions that come from aviation 

operations. However, tracking emissions from a wide variety of sources operating simultaneously, which 

are spread out over an airport, and which are being influenced by changing operating schedules and the 

dynamic effects of variable weather, is challenging. To make sense of all of the measurement data and 

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Aviation Emissions, Impacts & Mitigation: A Primer

information that has been gained about emissions, powerful tools have been developed that help to track 

and assess the impacts of aviation emissions.

Modeling Emissions and Exposure.

Computer models are the tools we use to assess environmental effects. The first models were simple and 

quantified emissions from individual sources. In the past decade, FAA has developed a suite of software 

tools that allow for a more thorough assessment of the environmental effects of aviation. NASA, Transport 

Canada, industry, and academia aided this multi-year development process.

The focus of this development effort has been to incorporate the best scientific understanding into the tools, 

by building on the body of data from the measurement programs. After quantifying emissions from 

multiple sources over a common time period, current models show how weather and other atmospheric 

conditions cause the emissions to migrate or disperse into the environment. Adding dispersion capabilities 

was a significant milestone in model development. Dispersion analysis allows the modeler to calculate the 

concentration of emissions at various points on and off the airport. This in turn shows the degree to which 

passengers, citizens living nearby, and the local community are exposed to aviation emissions.

Furthermore, these tools can provide a before-and-after comparison of pollutant concentrations for planned 

airport improvements as a way of demonstrating project impacts.

The primary building block of this new suite of software tools is the Aviation Environmental Design Tool 

(AEDT)30, which integrates existing noise and emissions models and helps assess interdependencies. 

AEDT is currently used by the U.S. Government for domestic planning, environmental compliance, and 

research analysis. Another element of the suite, targeted to the government research community, is the 

assessment of aircraft performance using tools such as Environmental Design Space (EDS)31 Piano (Project 

Interactive Analysis and Optimization)32, TASOPT (Transport Aircraft System OPTimization33, and 

SUAVE (Stanford University Aerospace Vehicle Environment)34. These tools are used to address different 

types of questions that are being asked. EDS is an aircraft and engine analysis tool capable of estimating 

source noise, exhaust emissions, performance and economic parameters for future aircraft designs under 

different technological, operational, policy, and market scenarios. EDS can assess interdependencies 

between noise, emissions, and performance at the aircraft level. PIANO is used to extract aerodynamic and 

performance data for aircraft manufactures that did not provide this data. TASOPT was used in PARTNER 

Project 48 35(Development of a Distributed Approach to System Level Uncertainty Quantification) in the 

creation of a new aircraft conceptual design capability in the FAA tools suite and in developing an 

approach to perform a system-level quantification of uncertainty. SUAVE is a design tool that allows for 

an arbitrary aerospace vehicle to be designed with an arbitrary level of fidelity in its supporting data. It was 

used in PARTNER Project 43 (Analysis of Mission Specifications).

36

This allows FAA to analyze fleet level impacts of future aircraft designs. To complete the suite of tools,

the Aviation Environmental Portfolio Management Tool (APMT) is under development. Initially targeted 

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Aviation Emissions, Impacts & Mitigation: A Primer

for government use, APMT adds environmental impact and economic analysis capabilities to the tool 

suite.

37

Each model in this environmental tools suite can be run independently, to allow focus on specific aspects of 

the analysis, but also can operate in an integrated fashion. This current suite of tools provides the ability to 

characterize and quantify aviation emissions, impacts on health and welfare, and industry and consumer 

costs, at local, regional, national and international levels. Users can assess different policy, technology, 

operational, and market scenarios and also evaluate the interdependencies between emissions and noise and 

understand the cost impacts. With this suite of models, different options for mitigating the impacts of 

emissions can be evaluated. For example, FAA can assess the environmental benefits of air traffic 

management system modernization alternatives, evaluate new engine and airframe designs, and assess 

health and economic impacts from the use of alternative fuels. The models also allow the FAA to 

coordinate with foreign counterparts through the International Civil Aviation Organization (ICAO), a 

United Nations intergovernmental body responsible for worldwide planning, implementation, and 

coordination of civil aviation, and ICAO’s Committee on Aviation Environmental Protection (CAEP).

38

Aviation Emissions and Air Quality.

Particulate matter, ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead are 

common air pollutants found in the atmosphere across the United States. These pollutants can harm human

health and the environment, and cause property damage. Of the six pollutants, particle pollution and 

ground-level ozone are the most widespread health threats. EPA regulates ground-level ozone, which is 

not emitted directly but is formed when nitrogen oxides and hydrocarbons react in the atmosphere in the 

presence of sunlight. Since 1980, total U.S. emissions of certain air pollutants EPA regulates (NOx, SOx, 

PM, CO, and lead (Pb)) have declined significantly, according to their 2012 report National Emissions 

Inventory (NEI) Air Pollutant Emissions Trends Data.

39 As shown in Figure 4, NOx decreased 46 percent, 

sulfur dioxide (SO2) emissions have decreased 63 percent, and emissions of particles less than 2.5 

micrometers (PM2.5 ) declined by 11 percent. At least half of these reductions occurred within the last five 

years. In spite of these successes, ground-level ozone and particles less than 2.5 micrometers (PM2.5

)

continue to present challenges in many areas of the country.40

Total national pollutant emissions do not tell the full story with regard to aviation’s contribution in regions 

with air quality problems. EPA data confirms that the worst air quality generally occurs in and around 

cities, which is also where aviation activity primarily occurs. The Clean Air Act, which will be discussed in 

further detail later in the document, requires EPA to determine whether regions within the U.S. comply 

with (i.e. attain) National Ambient Air Quality Standards (NAAQS).41 Many U.S. airports are in 

nonattainment areas: 43 of the 50 largest airports are in ozone (O3) nonattainment areas and 12 are in PM2.5

nonattainment areas.

42 Aviation’s contribution to a region’s air emissions inventory is generally small, as is 

shown in Table 2.

43

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Aviation Emissions, Impacts & Mitigation: A Primer

Figure 4: U.S. Pollutant Emissions from All Emission Sources

U.S. annual pollutant emissions44

According to the National Environmental Policy Act, airport construction projects that are funded with 

public dollars must not interfere with a region’s ability to attain the NAAQS. For capacity enhancing 

projects, emissions mitigation projects may be necessary for an airport expansion to proceed. Such projects 

may include converting airport shuttle buses and other vehicles to low emission alternative fuels such as 

compressed natural gas or electricity, installing gate electrification and preconditioned air services so that 

aircraft do not have to run their auxiliary power units when parked at the gate, or installing solar energy 

panels to produce electricity. 

In the past few years, scientists have hypothesized that aircraft emissions released at cruise altitude, 

particularly SOx and NOx, are likely to produce additional secondary PM that is transported very long 

distances (continent to continent) and then deposited to the surface of the Earth to affect air quality.

45

These results need to be confirmed to understand the significance of these emissions. FAA has several 

research projects underway to better understand the science and mechanisms involved and to quantify local 

air quality impacts from cruise emissions.

46

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Aviation Emissions, Impacts & Mitigation: A Primer

Aviation Emissions and Climate Change.

Concern regarding greenhouse gas emissions has been building worldwide. Total U.S. greenhouse gas 

emissions have increased at an average annual rate of 0.4 percent since 1990.47 Transportation emissions in 

the U.S. have increased about twice that fast and by 2012 accounted for about 28% of total U.S. CO2

emissions, as illustrated in Figure 5: U.S. Greenhouse Gas Emissions by Economic Sector. Aviation 

accounts for about 12% of transportation emissions, or 3.36% of total CO2 emissions in the U.S.

Figure 5: U.S. Greenhouse Gas Emissions by Economic Sector (2012) 48

Figure 6: Transportation Energy Use by Mode (2012)49

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Aviation Emissions, Impacts & Mitigation: A Primer

Similarly the latest global climate research indicates that aviation’s contribution to human-induced climate 

change is between 3.5% and 4.9%.

50 This share is forecast to increase to between 4.4% and 6.2%, by 

205051 unless new technologies and policies are adopted to reduce aviation emissions. There remains a 

great deal of uncertainty in estimated impacts on climate change, which is being resolved through ongoing

research efforts.

52

The climatic impacts of aviation emissions are quite complex and include direct climate effects from CO2

and water vapor emissions, the indirect effect on climate resulting from changes in the distributions and 

concentrations of O3 and methane (CH4) due to NOx emissions, the direct effects (and indirect effects on 

clouds) from emitted aerosols and aerosol precursors, and the climate effects associated with contrails and 

cirrus cloud formation.

Climate effects are due to interaction with solar and thermal radiation by gases such as carbon-dioxide and 

water vapor (see Figure 7 below), as well as pollutants such as CO, HC and black carbon (BC) particles 

arising from incomplete combustion in the gas turbine combustor. SOx emissions form sulfuric acid in the 

presence of water vapor, which further interacts with ammonia (NH3) in the Earth’s boundary layer to form 

ammonium sulfate particles. NOx emissions affect the formation of ozone and form nitric acid (HNO3) at 

cruise altitudes and ammonium nitrate particles in the boundary layer in the presence of ammonia, thus 

affecting air quality. The soot particles at cruise altitudes interact with other chemicals such as sulfuric 

acid and nitric acid to form small particles that act as nucleating sites for condensation of water vapor 

present in the upper atmosphere under certain conditions to form larger particles to form condensation trails 

or contrails, for short. These contrails are visible along flight tracks with a short lifetime around a few 

hours. At times, under the right meteorological conditions these contrails expand perpendicular to the 

flight tracks to form contrail-induced cirrus clouds that also interact with shortwave and longwave 

radiation, thus affecting climate.

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Aviation Emissions, Impacts & Mitigation: A Primer

 Figure 7: Schematic representation of emissions from aircraft combustion53

Atmospheric and climate system interactions (e.g. chemical, microphysical, dynamical and radiative) of 

aircraft emissions remain poorly understood and require more research. Figure 7 is a graphical 

representation of the current understanding of the potential climate and social welfare impacts of emissions 

from aircraft combustion.

The figure above also shows policy implications at various stages of these emissions, with increasing 

policy relevance downward. The formation of gases and particles that interact with radiation affect climate 

and air quality at the surface. Minimization of these products is therefore desirable. Mitigation options 

such as altering the routes to prevent formation of contrails, redesigning engine combustors with high 

bypass ratios to reduce temperatures to minimize formation of NOx, and reducing impurities such as sulfur 

in the fuel to minimize formation of particles are all examples of results of policy decisions to minimize 

climate impacts. Ultimately such actions result in reducing the costs to the society and increase social 

welfare in the form of impacts on health and wellbeing. 

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Aviation Emissions, Impacts & Mitigation: A Primer

Regulation of Aviation Emissions.

A wide range of environmental regulations applies to airport activity and equipment. Aircraft engines have 

certification requirements for CO, HC, NOx, and smoke emissions. Ground access vehicles are subject to 

tailpipe emission standards, and GSE may be subject to nonroad engine standards. The composition of jet 

fuel, diesel fuel, and gasoline are all regulated to limit harmful emissions, ensure proper performance of 

engines and fuel systems, and avoid engine durability concerns. The reduction in the level of sulfur in 

gasoline is justified by its known reduction in the efficiency of catalytic converters, which means these 

devices are less capable of removing emissions from exhaust gases. Thus, removing sulfur is a means of 

reducing other emissions of toxins from ground vehicle exhausts. Reduction of naphthalenes in fuel 

reduces the formation of carbonaceous particles that are potentially harmful, because they can cause 

erosion on turbine blades and form hot spots that can lead to premature engine failure. Many operational 

activities and equipment require permits. The FAA must consider the air quality impact of actions it 

undertakes, licenses, or funds and determine that airport expansion plans conform to regional air quality 

plans.

The Clean Air Act (CAA)54 is the primary, overarching air quality law in the U.S. The CAA establishes 

EPA as the agency responsible for setting appropriate air quality standards and developing regulations to 

meet those standards. EPA sets standards for ambient air quality in geographic regions that generally 

represent metropolitan areas. Under the CAA, EPA sets the NAAQS for NO2, SO2, PM2.5, CO, O3 and lead 

(Pb). EPA sets most regulatory standards but many permitting programs are administered by state 

agencies. With respect to aircraft engines, the CAA requires EPA to consult with the FAA and provides 

the FAA with the authority to enforce EPA’s aircraft engine emissions standards through its certification 

regulations.

55 FAA is responsible for ensuring these regulations do not pose conflicts with safety and other 

aircraft operational requirements. For example there are more than 60 standards56 that apply to aircraft 

engine design, materials of construction, durability, instrumentation and control, and safety, among others.

These are in addition to the Fuel Venting and Exhaust Emission Requirements for Turbine Engine Powered 

Airplanes,

57 which specify compliance with EPA’s aircraft exhaust emission standards.

The National Environmental Policy Act of 1969 (NEPA)58 requires federal agencies to consider the 

environmental impacts of their actions, which could include grants, loans, leases, permits and approval of 

plans or projects. NEPA applies to most airport construction projects as a result of FAA funding or 

approval. Some actions that are subject to NEPA review also trigger the CAA’s “general conformity” 

provision, which seeks to ensure that actions approved by the federal government do not interfere with a 

region’s plan to meet air quality standards.59 Federal agencies must ensure that proposed project emissions 

from Federal actions at airports located in nonattainment areas “conform” to the applicable State 

Implementation Plan.

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Aviation Emissions, Impacts & Mitigation: A Primer

Internationally, ICAO has long been the forum for evaluating the environmental performance of aircraft 

engines. ICAO has taken a “technology progressing” approach, raising standards within the capabilities of 

proven technologies and certified products (engines and aircraft) rather than a “technology forcing” 

approach, which would set standards based on technology that is not certified or may not even exist. The 

reason for ICAO’s approach is quite simple – the very high premium placed on the safety of aircraft 

operation restricts the use of unproven new technologies.

Health and Environmental Effects of Aviation Emissions.

Particulate Matter (PM).

The FAA continues to sponsor research60 to understand and evaluate how aviation emissions contribute to 

local and regional air quality, through a combination of measurement and modeling studies using the most 

advanced computer tools, and to evaluate the potential incremental health risks due to air pollutants such as 

particulate matter, ozone, and hazardous air pollutants. This research has built on the extensive health 

impacts research undertaken over many years by EPA and medical research organizations. Research to date 

indicates that fine particulate matter is responsible for the majority of the health risks from aviation 

emissions, although ozone also has a substantial health impact too. A comprehensive health impacts 

analysis should include the impacts of ozone and other pollutants as well.

61

Throughout the transformation process, particles form in various sizes. As a general rule, the smaller the 

particle the further it travels in the atmosphere, the longer it remains suspended in the atmosphere, and the 

more risk it poses to human health. Particulate matter includes both primary PM, which is directly emitted 

into the air, and secondary PM, which is formed through physical and chemical atmospheric processes. 

PM 2.5 can be readily inhaled and thus potentially pose increased health risks. These particles are too small 

to readily settle out of the atmosphere. They can be transported thousands of miles and remain in the 

atmosphere for days to weeks.

62 Additionally, fine particles suspended in the atmosphere absorb and 

reflect light, which is the major cause of reduced visibility (haze) in parts of the United States. Ultrafine 

particles are a subset of PM2.5, measuring less than 0.1 micrometer in diameter.

There are multiple health effects associated with exposure to PM, including impacts to the respiratory, 

cardiovascular, and neurological systems.

63 Smaller particles less than 2.5 micrometers in diameter, which 

are typical of aviation emission, tend to pose higher risk since they migrate deeper into the lungs and 

bloodstream causing cardiovascular effects and even affecting the nervous system. Human exposure to 

small particles can aggravate heart and lung disease resulting in increased hospital admissions, emergency 

room visits, and absences from school or work. Older adults, children, and people with heart or lung 

disease are the most sensitive to exposure to PM.

Preliminary research suggests that of the premature mortalities related to emissions from all combustion 

sources, less than 1% are associated with aviation emissions.

64 In the future, the relative health risks of 

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Aviation Emissions, Impacts & Mitigation: A Primer

aviation emissions will be strongly influenced by changing background pollutant concentrations and 

population growth as well as changing non-aviation emissions. 

EPA set the first PM standards65 in 1971. The standards were revised in 1987, 1997, 2006, and again in 

2013.

66 EPA no longer regulates particles larger than 10 micrometers (e.g., sand and large dust), which was 

the focus of the original standards, since they are not deemed readily inhalable. The local PM 

concentration is the sum of all regional sources of PM and the regional ambient background. PM emissions 

from airports and other regional sources mix relatively quickly with the ambient background PM. The 

combination of emissions from airports and other regional sources and ambient concentrations of PM result 

in a combined atmospheric PM loading that depends on complex atmospheric processes, including 

chemical reactions and pollution transport. This makes it difficult to isolate the contribution of airport 

activity from all other emissions sources in an area.

In addition to the CAA’s NAAQS there are other regulations that directly or indirectly effect PM emissions 

from aviation. For example, ICAO has established aircraft engine certification standards67 that limit smoke 

emissions, as measured by “smoke number.”68 The smoke standards took effect in 1983. Since smoke is 

an indicator of PM emissions, these standards have been indirectly influencing aircraft PM emissions for 

the past 30 years. 

As described earlier, sulfur in jet fuel combines with oxygen from the air during combustion, producing 

SO2, a portion of which eventually produces secondary particulate matter. Sulfur emissions are directly 

related to the sulfur content of the fuel. Internationally accepted standards69 for Jet A, which is the 

commercial aviation fuel used in the US, limit fuel sulfur content to 0.30% wt. (3,000 PPM S) maximum. 

In practice, however, weighted mean sulfur levels for Jet A sulfur measured in the 2010 survey are well 

below the typical maximum specification limit. The four month averaged weighted mean sulfur level on 

the overall U.S. was 544 PPMS, a 23% drop from the 2007 to the 2010 levels.70

EPA has required diesel fuel suppliers for nonroad equipment to reduce fuel sulfur content to the same 

ultra-low sulfur limits required for on-road diesel. This allows the nonroad equipment to use advanced 

emission control technologies. These requirements for diesel fuel sulfur limits and engine emission 

standards will reduce PM emissions from nonroad equipment by 90%.

71 GSE using alternative fuels such 

as compressed natural gas and propane have 25% lower PM emissions72 and those powered by electricity73

have no PM emissions.

In 2007, EPA proposed new exhaust emission standards74 for non-road diesel engines. These standards are 

being phased in between 2008 and 2014 and require engine manufacturers to produce new engines with 

advanced emission control technologies. New GSE with diesel engines are required to meet these 

standards. This new equipment achieves emission performance comparable to today’s automobiles.

Stationary emission sources at airports include various facilities and equipment like boilers, emergency 

generators, incinerators, fire training facilities, and fuel storage tanks. Many of these equipment types 

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Aviation Emissions, Impacts & Mitigation: A Primer

require specific operating permits with PM emission limits. Stationary sources typically represent about 1-

2% of PM emissions at airports.

75 Individual particle species that do not appear to be harmful may be so 

when occurring in a mixture. PM can be solids, like dust, ash, or soot, and it can also be completely liquid 

aerosols or solids suspended in liquid mixtures.76 Measures to reduce particles will reduce all components 

of the mixtures. Batteries of scientific studies have linked particulate matter, especially fine particles either 

alone or in combination with other air pollutants, with a series of significant health problems. The relation 

to adverse health effects has made fine particulate matter of primary concern in aviation studies. These are 

topics for ongoing and future research.

77

Oxides of Nitrogen (NOx).

ICAO has established international certification limits78 for oxides of nitrogen (NOx) emissions from jet 

engines that limit the amount of NOx emitted. EPA has adopted ICAO’s certification standards as national 

regulations.

79 FAA, in turn, enforces these standards through engine certification.

Current NOx emission standards for aircraft engines were established in 201280, which is a tightening of the 

prior standards. This is the fourth change since the original standards were agreed to in 1981. New 

standards went into effect for engines entering service beginning in 2013, which reflect a 12 percent NOx

reduction over the 2008 standards. ICAO’s CAEP has since recommended new certification standards that 

represent a further 15 percent NOx reduction, with an effective date of 2014.

81 For aircraft, new NOx

certification standards are being considered that will reduce their total NOx emissions. Aviation NOx

emissions are still projected to be less than 3 percent of the transportation NOx inventory by 2020.

82

While there currently are no national or international regulations for greenhouse gas emissions that apply to 

aircraft or other airport sources, the aviation industry has made significant strides here as well. Aircraft 

have a long history of continuously improved fuel efficiency (measured in fuel use per passenger mile), 

which reduces all greenhouse gas emissions. For example, according to Boeing, the Boeing-787 is 20 

percent more efficient than the Boeing-767, which it succeeds83 and the Boeing-737N (the Max) burns 14% 

less fuel than today’s Beoing-737-800NG.

84 Fuel efficiency and energy conservation are also priorities at 

many airports.

85

Future Regulations.

The FAA is working through ICAO to evaluate policy options to limit or reduce greenhouse gas emissions 

from international aviation. ICAO has developed a range of standards, policies and guidance material for 

the application of integrated measures to address aircraft noise and engine emissions. Efforts include 

progress on new aircraft technology advancement, operational improvements and development and 

deployment of alternative fuels, as well as a commitment to develop a global market-based measure for 

international aviation and appropriate airport and land-use planning. Through the ICAO’s CAEP, FAA is 

supporting development of an aircraft CO2 emission standard. The standard is expected to reduce aircraft 

CO2 emissions by integrating fuel-efficient technologies into aircraft design and development. It has been 

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Aviation Emissions, Impacts & Mitigation: A Primer

developed such that effective improvements observed through the CO2 standard will correlate with 

reductions of CO2 emissions by aircraft during day-to-day operations. CAEP is developing an aircraft 

engine PM certification standard as well. 

In October 2013, the 38th ICAO Assembly adopted a comprehensive climate change resolution that 

includes a commitment to develop a global market-based measure to address GHG emissions from 

international aviation. The U.S. is committed to pursuing development of a global market-based measure 

(MBM) proposal. It has to be considered as gap filler in the basket of measures that includes technology, 

operations and alternative fuels. These efforts contribute to achieving ICAO’s aspirational goal of carbon 

neutral growth by 2020 using a 2005 baseline. The U.S. is engaged both in supporting policy and technical 

work contributing to the proposal for a global MBM.

Under this multidimensional regulatory and voluntary structure, aviation has made significant 

environmental progress. Given the complexity of the industry and the need for different strategies and 

technological approaches for different types of vehicles and equipment, a coordinated effort will continue

between the aviation industry and the many regulatory agencies that share environmental responsibilities.

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Aviation Emissions, Impacts & Mitigation: A Primer

Mitigating Aviation Emissions

The efficiency of each part of the National Airspace System (NAS) affects the production, and resultant 

impacts, of aviation emissions. Each of the NAS parts -- aircraft operations, aircraft materials and 

technologies, and fuel composition -- has made significant advances in mitigating emissions over the past 

decade. Regulations are in place to limit harmful effects of aviation emissions on human health and the 

environment. The FAA, in working closely with industry and other government agencies, continues to 

invest significant resources into research and technology development to improve emissions mitigation. 

This section describes FAA’s approach to addressing environmental concerns and details some of the 

future research and development activities.

STRATEGY FOR REDUCING AVIATION EMISSIONS – Five-Pillar Environmental Approach.

FAA sets its specific goals for environmental initiatives based on the latest scientific understanding of 

aviation’s environmental impacts. The Agency relies on a five-pillar comprehensive and integrated 

approach to set the specific initiatives needed to achieve aviation environmental goals. 

PILLAR 1: Improved Scientific Knowledge and Integrated Modeling. 

Aviation environmental analyses, impact determinations, and mitigation decisions for NextGen activities 

must be based on a solid scientific foundation. This requires continued investments in research to improve 

scientific understanding of the impacts of aviation. In addition, developing and using advanced decisionsupport tools that account for interdependencies of impacts and cost-benefit analyses of potential solutions 

facilitates more informed decision-making. Prospective solutions and combinations of solutions have 

different impacts, benefits, and costs. Some solutions optimize for one area of environmental protection at 

the expense of another; where trade-offs are made they are explicitly defined and as transparent as possible.

Centers of Excellence (COE). The FAA has long had a successful partnership with the nation’s academic 

research community, working with more than 75 U.S. colleges and universities to foster important research 

conducted by faculty and students. For almost two decades, these efforts have contributed significantly to 

advancing aviation science and technology while providing the agency and the industry a high return on 

investments. Through FAA COEs, the government, academic institutions, and industry leverage the 

combined resources available for aviation research and maximize technological competence for public 

purpose. 

Alternative Fuel Effects on Contrails and Cruise Emissions (ACCESS). NASA initiated the ACCESS 

program as a follow-on to the APEX emissions measurement projects as part of their Fundamental 

Aeronautics Aviation Emissions Research program. With FAA’s active participation, the first ACCESS 

project sampled aircraft cruise emissions with inflight testing of a 50/50 blend of an alternative jet fuel and 

conventional jet fuel. Tests were conducted over a range of power-settings at different altitudes. Also 

extensive measurements of ice particle size and concentrations were made to evaluate contrail formation.

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Aviation Emissions, Impacts & Mitigation: A Primer

Additional alternative jet fuel testing and inflight emissions measurements will be part of future ACCESS 

projects conducted in the next few years. These projects may also provide an opportunity to verify the 

models used to evaluate aviation emissions impacts.

Aviation Emissions Characterization (AEC) Roadmap. The AEC Roadmap is a unified regulatory research 

and development (R&D) roadmap for understanding and quantifying aircraft emissions. FAA, NASA, 

DOD, and EPA all are members of the AEC Roadmap Coordination Council. There is collaboration on the 

roadmap with manufacturers, airports, airlines, and other stakeholders. The Roadmap coordinates research 

activities and communicates research findings among stakeholders and other parties with an interest in PM,

hazardous air pollutants (HAP), and other emissions from aviation sources. The Roadmap’s objective is to 

gain the necessary understanding of emissions’ formation, composition, and growth and transport 

mechanisms to assess aviation’s emissions and understand their impact on human health and the 

environment. The AEC Roadmap does not fund research projects but it does help agencies identify 

research priorities and leverage their budgets to accomplish more than they would otherwise. 

Airport Cooperative Research Program (ACRP). FAA funds an industry-driven, applied research program 

that develops near-term, practical solutions to problems faced by airport operators. The Transportation 

Research Board (TRB) of the National Academy of Sciences manages ACRP. The program carries out 

applied research on problems that are shared by airport operating agencies, which may not be adequately 

addressed by other federal research programs. A substantial number of ACRP projects have addressed 

environmental concerns ranging from emissions measurement campaigns to model development and 

enhancement to practical guidance to airports for improving their environmental performance. Of FAA’s 

$15 million annual funding for the ACRP, $5 million is allocated for environmental projects. Since the 

ACRP is identified in FAA reauthorization legislation,

86 it is anticipated that this program will continue in 

the future. 

Aviation Climate Change Research. In 2010, FAA initiated the 3-year Aviation Climate Change Research 

Initiative (ACCRI) program under its climate change research program to evaluate the impacts of aviation 

emissions on climate change from a 2006 baseline and into the future (2050). It evaluated the effects of 

aerosols, induced contrail effects, contrail-induced cirrus effects, and aerosol indirect effects. In addition to 

the tools FAA developed, this research used a number of large-scale general circulation models and simpleclimate models, satellite and laboratory measurements, and detailed aerosol and ice-particle microphysical 

models. This research recognized the potential impact of indirect aerosol and contrail effects. Quantifying 

these impacts is the subject of ongoing current climate research.

87 The current scientific opinion as 

expressed in this effort emphasizes the need to lower uncertainties while characterizing the aviation 

chemical and physical impacts on climate. Additional studies are currently underway in analyzing data 

from 2012 to estimate their reliability and accuracy.

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Aviation Emissions, Impacts & Mitigation: A Primer

PILLAR 2: Air Traffic Management Modernization. 

Developing and integrating advanced operational procedures and infrastructure improvements enhances 

operational capabilities that function more efficiently, improving energy efficiency and thus mitigating 

environmental impacts. Air traffic management modernization and improvements being made as part of 

NextGen increase the efficiency of aircraft operations, both in the air and on the airport surface. Improving 

efficiency saves time and fuel. Reducing fuel consumption reduces CO2 emissions that affect climate and 

other emissions that adversely affect air quality. Performance Based Navigation (including area navigation 

(RNAV) and required navigation performance (RNP)) routes can cut fuel burn, emissions, and flight times. 

Optimized Profile Descents (OPD) can reduce noise, emissions, and fuel consumption. New technology 

and procedures that optimize gate-to-gate operations are being demonstrated with international partners in 

Europe and Asia-Pacific to reduce fuel burn, emissions, and noise. One of the most significant programs 

for improving operations is NextGen. 

Transforming the Air Transportation System – NextGen. FAA has begun the transformation of the air 

transportation system through NextGen a metamorphosis of the air traffic control system. The FAA’s 

environmental vision for NextGen is to provide environmental protection that allows sustained aviation 

growth. NextGen will provide many opportunities for accomplishing emission mitigation goals by giving 

impetus to and accommodating changes that are needed for system efficiency and operational 

improvements. FAA is developing NextGen capabilities that will guide and track aircraft more precisely 

and efficiently in the air and on the ground to save fuel, decrease emissions and manage the impact of noise 

on communities. In addition, the Agency is advancing efforts to reduce aircraft fuel burn, emissions, and 

noise through innovative aircraft technologies. In this way, FAA’s environmental goals mesh well with the 

broader agency goals.

PILLAR 3: New Aircraft and Airport Technologies.

Historically, new technologies have offered the greatest success in reducing aviation’s environmental

impacts. New engine and airframe technologies continue to play key roles in achieving aviation 

environment and energy goals. The FAA and other agencies support advances in engine technology and 

airframe configurations to lay the foundation for the next generation of aircraft. Its technological strategy 

envisions a fleet of quieter, cleaner aircraft that operate more efficiently with less energy. The FAA and 

NASA, along with the Department of Defense, closely coordinate efforts on aeronautics technology 

research through the National Aeronautics Research and Development Plan. Each agency focuses on 

different elements but they share the same national goals. The FAA’s focus is on maturing technologies for 

near term application while NASA focuses on a broader range of time frames of technology development. 

FAA’s Continuous Lower Energy, Emissions and Noise (CLEEN) program is a NextGen effort to 

accelerate development and commercial deployment of environmentally promising aircraft technologies 

and sustainable alternative fuels. The aircraft technologies focus on reduction in aircraft noise, emissions, 

and fuel burn. Under this program, FAA has awarded five-year agreements to Boeing, General Electric, 

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Aviation Emissions, Impacts & Mitigation: A Primer

Honeywell, Pratt & Whitney, and Rolls-Royce. The total federal investment is expected to be $125 million 

over five years.

Continuous Lower Energy, Emissions, and Noise (CLEEN). The CLEEN program is a five-year effort to 

accelerate technology development. Advancements from the program reduce aircraft emissions, fuel burn, 

and noise through a cost shared initiative between FAA and industry where companies provide at least 50% 

or greater funding. 

CLEEN has demonstrated engine technology that reduced landing and takeoff NOx emissions by more than 

60 percent below the ICAO standard adopted in 2004. It is also developing aircraft technology that 

contributes toward a 33% aircraft fuel burn goal relative to current technology with commensurate energy 

consumption and greenhouse gas emission reductions. Improved engine technologies, avionics, aircraft 

aerodynamics, and weight-related technologies also are being developed that will reduce aircraft fuel burn 

further. These achievements are expected to appear in the commercial airline fleet in the next several years.

CLEEN has also made significant contributions in the development and deployment of alternative jet fuels 

that are a drop-in replacement to fuels derived from petroleum. Alternative jet fuels are being tested to 

confirm the environmental benefits, technological feasibility, and economic cost. The efforts of CLEEN on 

aircraft technology maturation and alternative fuels development and deployment will help the FAA ensure 

that NextGen provides environmental protection that allows sustained aviation growth.

Following the success of the CLEEN program to date, FAA has established new goals for a second phase 

program, CLEEN II, from 2015 to 2020. CLEEN II will again have components focusing on emissions, 

fuel burn, and noise. New technologies, new aircraft designs, new system designs, and new alternative fuels 

from this program are expected to appear in use in the commercial fleet beginning at the end of this decade 

and will achieve reduced emissions, fuel burn, and noise in the decades to come. 

Voluntary Airport Low Emission (VALE) program and Zero Emission Airport Vehicle and 

Infrastructure Pilot Program (ZEV). The FAA’s Office of Airports has two specific programs underway 

to reduce emissions from ground support equipment and other airport vehicles. The VALE program88

expands eligibility for airport low emission projects under the Airport Improvement Program (AIP) and the 

Passenger Facility Charges (PFC) program. Through the use of funding and emission credit incentives, the 

voluntary program supports converting airport vehicles and ground support equipment to low emission 

technologies, modifying airport infrastructure for alternative fuels, providing terminal gate electricity and 

air for parked aircraft, a pilot program to explore retrofit technology for airport ground support equipment, 

and other related emissions improvements. Between 2005 and 2012, more than $146 million89 from AIP, 

PFC, and local matching funds has been invested thorough the VALE program to reduce airport emissions.

The ZEV program90 allows FAA to award AIP funds to airports to purchase zero emissions vehicles and 

make infrastructure changes necessary to charge or otherwise fuel these vehicles. Authorized in 2012, the 

ZEV program encourages the use and development of electric and hydrogen fuel cell vehicles. There are a 

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Aviation Emissions, Impacts & Mitigation: A Primer

wide variety of vehicles used at airports, from automobiles and vans to large passenger buses, and this 

program encourages manufacturers to develop zero emission alternatives to meet these needs. 

PILLAR 4: Sustainable Alternative Aviation Fuels.

Developing and deploying sustainable alternative aviation fuels enables environmental improvements, 

energy security, and economic stability for aviation. The aviation industry is committed to converting its 

fuel supply to alternative fuels.91 Government and industry are working cooperatively with coordinating 

mechanisms such as the Commercial Aviation Alternative Fuels Initiative (CAAFI) and are supporting 

alternative fuels research. Near term efforts include adding new classes of fuels to the approved alternative 

jet fuel standard by American Society for Testing and Materials (ASTM) International and conducting 

aircraft flight tests using alternative fuels to confirm their suitability and environmental benefits. To date, 

these efforts have led to the certification of three alternative jet fuel types by ASTM International. ASTM 

International D7566 specification92 covers the manufacture of aviation turbine fuel that consists of 

conventional and synthetic blending components.

To date, three alternative jet fuels have been approved for blending with jet fuel by standard setting 

organization ASTM International. They include fuels from biomass, coal or natural gas known as FischerTropsch (FT) jet fuel; fuel from fats, plant oils and greases known as Hydroproccessed Esters and Fatty 

Acids (HEFA) jet fuel; and, fuel from fermented sugars known as Synthesized Iso-Paraffins (SIP) jet fuel. 

At this time additional fuel types are under evaluation for future approval.

One of the hallmark efforts in this area is Farm to Fly, commenced in July 2010,as a result of the U.S. 

Department of Agriculture (USDA), Airlines for America, Inc. (A4A), and the Boeing Company (Boeing) 

signing a resolution formalizing their commitment to work together on the initiative. The FARM to FLY

2.0 program93 will “accelerate the availability of a commercially viable and sustainable aviation biofuel 

industry in the United States, increase domestic energy security, establish regional supply chains, and 

support rural development.” In April 2013, the USDA and FAA joined with industry partners from 

Airlines for America (A4A), Aerospace Industries Association (AIA), Airports Council-North America 

(ACI-NA), National Business Aviation Association (NBAA) and the General Aviation Manufacturers 

Association (GAMA) in an expanded “Farm to Fly 2.0” collaboration “to enable commercially viable, 

sustainable bio-Jet Fuel supply chains in the U.S. that are able to support the goal of one billion gallons of 

bio-Jet Fuel production capacity and use for the Aviation Enterprise by 2018. In July, 2014 the U.S. DOE 

also signed on as a partner to the agreement.

Commercial Aviation Alternative Fuels initiative (CAAFI). CAAFI94 is a coalition of airlines, aircraft and 

engine manufacturers, energy producers, researchers, international participants, and U.S. government 

agencies formed to develop and deploy alternative jet fuels for commercial aviation. CAAFI’s goal is to 

develop alternative jet fuel options that offer equivalent levels of safety and compare favorably on cost with 

petroleum based jet fuel, while also offering environmental improvement and security of energy supply for 

26
Aviation Emissions, Impacts & Mitigation: A Primer

aviation. To date, CAAFI has seen three fuel development pathways approved by ASTM and more than 

1500 international demonstration and commercial aircraft flights using alternative fuels. Since aviation is 

international in scope, highly integrated in its fuel supply chain, and has a significant ability to align and 

coordinate within the industry, it is a very promising first mover among customers for alternative fuels.

Unleaded Avgas Transition (UAT Plan). Almost all aviation gasoline (avgas) used to power piston engine 

general aviation aircraft is designated “100 low lead.” 100 low lead contains small amounts of tetraethyl 

lead, which boosts fuel octane. High-octane fuels are required in many aircraft so that their piston engines 

will not “knock,” which can cause severe engine damage. However, EPA and the Centers for Disease 

Control and Prevention (CDC) have found in the past decade that there is no safe level of lead in blood. For 

that reason, the aviation community and government are coming under pressure to eliminate lead emissions 

from aircraft. At the request of the aviation, petroleum, and other concerned interests, FAA has initiated 

and is implementing the UAT Plan, which calls for a two-phase approach to identifying and approving an 

operationally safe unleaded avgas. One component of the plan is formation of the Piston Aircraft Fuels 

Initiative, which is composed of members from FAA, general aviation industry, and petroleum interests 

who will fund and coordinate identification and approval of the most promising unleaded candidate fuels. 

At the same time EPA is working to gain a better understanding of aircraft lead emissions and potential 

exposure through monitoring, modeling, demographic, and other studies. FAA’s goal is to have a 

replacement fuel for leaded avgas available by 2018,

95 which is usable by most general aviation aircraft.

PILLAR 5: Policies, Environmental Standards, and Market-Based Measures.

Developing and implementing appropriate policies, standards, programs, and mechanisms are critical steps 

in quickly integrating advantageous technology and operational innovations into the commercial fleet, the 

airport environment, and entire national aviation system. An example is the development of the NextGen 

Environmental Management System (EMS), which integrates environmental protection objectives into 

NextGen. Cooperative partnerships between government and industry focus effort and leverage funding in 

ways that are beneficial for aviation and good for the environment. Internationally, the U.S. is leading 

efforts at ICAO to limit and reduce international aviation emissions, most notably through development of 

an aircraft CO2 standard and an engine PM certification requirement. ICAO has additionally agreed to 

explore more ambitious goals for the aviation sector including carbon neutral growth in the mid-term and 

reductions in the long term. The FAA is exploring the effectiveness of various policies, including economic 

incentives to limit and reduce CO2 emissions. Additionally, to achieve environmental and energy goals 

beyond the near term, policies are needed that accelerate the integration of new technologies into the civil 

fleet compared to the normal rate of introduction and replacement.

Aviation Sustainability Center (ASCENT). FAA recently established a new Center of Excellence for 

Alternative Jet Fuels and Environment. ASCENT will explore ways to meet the environmental and energy 

goals for NextGen, which will provide environmental protection that allows sustained aviation growth. 

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Aviation Emissions, Impacts & Mitigation: A Primer

ASCENT is structured as a cost sharing partnership with academia to provide R&D support to inform 

FAA’s environmental commitments and aspirational goals. 

To achieve the aspirational 2018 alternative jet fuels target of one billion gallons used96 per year and help to 

ensure the wide spread use of sustainable alternative jet fuels in the longer term, ASCENT will assist the 

FAA and the community with research to develop viable supply as well as secure ASTM International 

approval of alternative jet fuels.

Partnership for Air Transportation Noise and Emissions Reduction (PARTNER). PARTNER, an FAA 

COE, was cosponsored by NASA, Transport Canada, the U.S. Department of Defense, and the U.S. 

Environmental Protection Agency. PARTNER was comprised of 12 universities,

97 and approximately 50 

advisory board98 members including aerospace manufacturers, airlines, airports, national, state and local 

government, professional and trade associations, non-governmental organizations and community groups. 

They were united to foster collaboration and consensus to jointly advance environmental performance, 

efficiency, safety and security.

As an incentive to collaboration, equal matches were required for federal funds granted to PARTNER. The 

universities provided some of these matching funds, but most were obtained from the organizations 

represented on the advisory board. This collaborative process fueled unique research efforts on emissions, 

operations, alternative fuels, noise, and policy evaluations involving a wide spectrum of participants. More 

than 48 research projects have been completed or are underway representing a total budget of more than 

$56 million over the past 10 years. With the completion of the PARTNER program, a new Center of 

Excellence, ASCENT, was established. Some of the PARTNER projects were transitioned, through a 

competitive process to ASCENT, discussed above. 

Reducing Aviation Emissions in the Future.

FAA has made significant progress addressing environmental concerns through the strategy and programs 

it has created under the Five Pillar Environmental Approach. New engine designs and technologies, like 

those developed in the CLEEN program, are improving fuel efficiency further, while simultaneously 

reducing noise, NOx and PM emissions. New aircraft designs are taking advantage of advanced computer 

models to improve operating performance and fuel efficiency, reducing all pollutants at the same time. New 

air traffic control technologies and operating practices are reducing emissions by reducing fuel 

consumption. Airports are using low emission equipment. And alternative jet fuels are being developed that 

will cut the impact of aviation on climate change and air quality significantly. More progress in reducing 

environmental impacts will be needed, however, to meet the challenges of the future posed by growth in 

aviation and the need to reduce emissions beyond current levels, particularly with respect to climate 

emissions.

It is clear that aviation emissions’ impacts on health and the global climate will drive the FAA’s research 

program in the future. These impacts are continually interpreted through regulatory and policy mandates, 

28
Aviation Emissions, Impacts & Mitigation: A Primer

such as the Clean Air Act, the National Environmental Policy Act, FAA’s NextGen program, and ICAO 

requirements, which in turn set new levels of performance that must be achieved. Those mandates are 

evaluated using the Five-Pillar Environmental Approach to define research plans and objectives as noted in 

Figure 8: Defining Research Initiatives.

Figure 8: Defining Research Initiatives

FAA has set ambitious goals for the future. As expressed in the Aviation Environmental and Energy Policy 

Statement,

99 FAA’s air quality goal is to achieve an absolute reduction of significant health and welfare 

impacts attributable to aviation, notwithstanding aviation growth. The Agency’s climate goal is to limit the 

impact of aircraft CO2 emissions on the global climate by achieving carbon neutral growth by 2020 

compared to 2005 (i.e., zero growth in CO2 emissions) and to achieve a net reduction of the climate impact 

from all aviation emissions by 2050. The energy efficiency goal of the US is to achieve at least 1 percent

per year improvement in the energy efficiency of the National Airspace System. The FAA also recognizes

ICAO’s aspirational energy goals for international aviation as 2 percent improvement per year. Taken 

together, these goals represent a significant improvement in aviation’s environmental performance but will 

take an ambitious R&D program to accomplish.

29
Aviation Emissions, Impacts & Mitigation: A Primer

Planning is underway for CLEEN II with new, demanding goals for new technologies, new aircraft designs, 

new system designs, and new alternative fuels. New emissions measurement projects such as ACCESS in 

concert with NASA and collaborations with the international community developing particulate matter and 

CO2 engine emission standards are envisioned. Emissions models must be have their dispersion modeling 

capabilities upgraded to meet the more demanding information required to fully understand health risks. 

FAA desires a better understanding of the interdependencies of emissions and noise and their interrelated 

impacts. And much more information is needed to understand the climate impacts of non-CO2 aviation 

emissions.

The FAA cannot achieve these ambitious goals alone. Continued cooperation with other Federal agencies 

such as NASA, EPA, DOD, DOE, and USDA, as well as collaboration with corporations and industry 

associations, and the scientific community will be essential.

Achieving research goals will allow the aviation industry to significantly reduce its environmental impacts

and begin to reduce its total emissions of PM, NOx, and CO2. This takes time, however. As noted earlier it 

takes 20 years for 86% of the fleet to achieve current new technology performance. This also assumes that 

funding will be available to continue current projects and to support new projects as planned. 

The FAA Modernization and Reform Act of 2012 (FAA Reauthorization)100 stipulated that an independent, 

outside panel of experts review energy-related and environment-related research programs. The review was 

conducted during the summer of 2013101 to determine whether the programs (1) have well-defined, 

prioritized, and appropriate research objectives; (2) are properly coordinated with research programs at 

NASA, National Oceanic and Atmospheric Administration (NOAA), and other relevant agencies; (3) have 

allocated appropriate resources to the research objectives; and (4) have mechanisms for transitioning the 

results into FAA’s broader activities.

The independent panel review found that FAA’s research is well defined, effectively prioritized, and has 

relevant objectives. They also found the research is well coordinated with other agencies and significant 

efforts have been made to transition research to other parts of FAA. However, “funding is, and will 

continue to be, a major constraint on the ability of the FAA to achieve its energy and environmental 

goals.” They further stated that, at current levels of funding, the programs have allocated appropriate 

resources to achieve research objectives yet given potential reductions in future funding levels, the 

achievement of research goals may be put in jeopardy. Further federal investment in aviation research and 

technology development will be essential to meet the government’s commitment.

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Aviation Emissions, Impacts & Mitigation: A Primer

Conclusion 

Aviation is a complex and vital industry serving not only the U.S. but also the entire world. It supplies 

tremendous economic benefits to those countries that embrace it. Its speed and accessibility are well suited 

to modern society as globalization, technology development, and just-in-time manufacturing transform the

world. To maintain its central transportation role, aviation must ensure it can mitigate any environmental 

constraints that result from its operations.

There are features that distinguish aviation from other transportation modes and industries that must be 

factored into environmentally-motivated strategies. Aviation places a high premium on safety, which

demands the incorporation of only proven and technically sound technologies to reduce environmental 

impacts. Aircraft are high cost and have a long life span, requiring long lead times for new technologies to 

be widely incorporated in the fleet. Airframe and engine manufacturers as well as airlines will need to 

invest the capital to build and operate aircraft with new technologies for aviation to realize the 

environmental and operational benefits. Airport infrastructure requires substantial planning and 

construction effort, as well as public and financial support. Such considerations increase the challenge of 

achieving the ambitious environmental and energy performance expectations envisioned in the NextGen 

transformation of the U.S. aviation system. 

Within this framework of constraints, aviation has safely and progressively improved its environmental

performance. This commitment to operating in balance with the environment and in support of beneficial 

environmental mitigation practices are forcefully stated in the FAA’s Aviation Environmental and Energy 

Policy Statement, as further advanced by the Aviation Greenhouse Gas Emissions Reduction Plan102. Fuel 

economy, which is one strong indicator of environmental performance, has consistently improved. Aircraft 

engines have gotten more efficient and been designed with environmental performance in mind. Regulatory 

frameworks have developed to constrain emissions growth from many aviation sources. Improvements to 

the efficient operation of the complex aviation network have had a positive effect on the environment. And 

new fuels are being developed to reduce harmful emissions as well as aviation’s impact on climate change. 

Much of this progress is a direct result of the research conducted in the programs planned and managed by 

FAA’s Office of Environment and Energy. 

FAA, together with EPA and NASA, is committed to ensuring aviation emissions do not pose human 

health risks, degrade the global climate, or restrain aviation’s mobility and economic benefits enjoyed by 

society. Its consistent, coordinated effort and continuing success in technology research and development 

will ensure NextGen’s goals can be met and environmental goals can be achieved. And the broad inclusion 

and sustained commitment to working with all stakeholders will ensure the U.S. will be a global leader in 

researching, developing, and implementing technological, operational, and policy initiatives that address 

both aviation’s growth opportunities and environmental challenges.

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Aviation Emissions, Impacts & Mitigation: A Primer

Looking to the future, FAA has the strategic framework in place for planning and implementing an 

emissions research roadmap for continuing to mitigate the environmental impacts of aviation emissions. 

This includes continuing to improve understanding of the role of aviation emissions on health impacts on 

the surface of the Earth as well as climate change. FAA is working with industry and other stakeholders to 

advance the performance of the national and international aviation system as well as to improve individual 

system components. For example within ICAO, the FAA continues to work on a comprehensive basket of 

solutions to mitigate aviation noise and emissions impacts while simultaneously working to improve energy 

efficiency and security. The U.S. is committed to pursuing development of a global MBM for international 

aviation through ICAO. The global MBM is considered gap filler in the basket of measures that includes

improvements in technology, operations and sustainable alternative fuels to achieve carbon neutrality for 

the world-wide aviation industry.

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Aviation Emissions, Impacts & Mitigation: A Primer

Abbreviations & Acronyms

ACCESS – Alternative Fuel Effects on Contrails and Cruise Emissions

ACCRI – Aviation Climate Change Research Initiative

ACRP – Airport Cooperative Research Program

AEC – Aviation Emissions Characterization Roadmap

AEE – Office of Environment and Energy

AIP – Airport Improvement Program

APEX – Aircraft Particle Emissions Experiment

APU – Auxiliary Power Unit

ASCENT – Aviation Sustainability Center

ASTM – American Society for Testing and Materials

BC – black carbon

BTU – British Thermal Unit

CAA – Clean Air Act

CAAFI – Commercial Aviation Alternative Fuels Initiative

CAEP – Committee on Aviation Environmental Protection

CCR – Climate Change Research

CDC – Centers for Disease Control and Prevention

CH4 – methane

CLEEN – Continuous Lower Energy, Emissions, and Noise

CO – carbon monoxide

CO2 – carbon dioxide

COE – Center of Excellence

EMS – Environmental Management System

EPA – Environmental Protection Agency

FAA – Federal Aviation Administration

GDP – gross domestic product

GSE – ground support equipment

HAP – hazardous air pollutant

HC – hydrocarbon

HNO3 – nitric acid

H2O – water

H2SO4 – sulfuric acid

ICAO – International Civil Aviation Organization

LTO – Landing Take Off

MBM – Market-Based Measure

33
Aviation Emissions, Impacts & Mitigation: A Primer

N2 – nitrogen

NAAQS – National Ambient Air Quality Standards

NASA – National Aeronautics and Space Administration

NEPA – National Environmental Policy Act

NextGen – Next Generation Air Transportation System

NH3 – ammonia

NH4NO3 – ammonium nitrate

(NH4)2SO4 – ammonium sulfate

N2O – nitrous oxide

NOAA – National Oceanic and Atmospheric Administration

NO2 – Nitrogen dioxide

NOx – nitrogen oxides

O2 – oxygen

O3 – ozone

OPD – Optimized Profile Descents

PARTNER – Partnership for AiR Transportation Noise and Emissions Reduction

Pb – lead

PFC – Passenger Facility Charges

PM – particulate matter

PM2.5 – particulate matter 2.5 microns and smaller

R&D – research and development

RNAV – area navigation

RNP – required navigation performance

S – sulfur

SO2 – sulfur dioxide

SOx – sulfur oxides

TRB – Transportation Research Board

UHC – unburned hydrocarbons

UAT – United Avgas Transition Plan

VALE – Voluntary Airport Low Emission Program

VOC – volatile organic compound

ZEV – Zero Emission Airport Vehicle and Infrastructure Pilot Program

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Aviation Emissions, Impacts & Mitigation: A Primer

End Notes

1 http://www.atag.org/facts-and-figures.html 2 Ibid

3 Transportation Energy Data Book, US Department of Energy, Edition 33, July 31, 2014 

http://cta.ornl.gov/data/index.shtml

4 http://www.faa.gov/about/office_org/headquarters_offices/apl/environ_policy_-

guidance/policy/media/FAA_EE_Policy_Statement.pdf

5 http://www.faa.gov/about/office_org/headquarters_offices/apl/research/science_integrated_modeling/

6 http://www.faa.gov/airports/environmental/environmental_desk_ref/media/desk_ref_chap20.pdf 7 Simone, N.W., et al. Rapid estimation of global civil aviation emissions with uncertainty quantification. 

Transport. Res. Part D (2013), http://dx.doi.org/10.1016/j.trd.2013.07.001 8 Based on mass balance analysis using emission factors from the ICAO Aircraft Engine Emissions 

Databank for representative aircraft engines http://easa.europa.eu/document-library/icao-aircraft-engineemissions-databank 9 Conversion Factors for Hydrocarbon Emission Components, US EPA. Some hydrocarbons are less 

ozone-forming than other hydrocarbons, so EPA has officially excluded them from the definition of 

regulated hydrocarbons called volatile organic compounds (VOC). This definition excludes methane, 

ethane, acetone, and compounds not commonly found in large quantities in engine exhaust like 

chlorohydrocarbons from consideration as VOC.

10 Jathar, S.H., et al, Modeling the formation and properties of traditional and non-traditional secondary 

organic aerosol: problem formulation and application to aircraft exhaust, Atmospheric Chemistry and 

Physics, 12, 9025–9040, 2012 <http://www.atmos-chem-phys.net/12/9025/2012/acp-12-9025-2012.pdf> 11 Jathar, S.H., et al, Modeling the formation and properties of traditional and non-traditional secondary 

organic aerosol: problem formulation and application to aircraft exhaust, Atmospheric Chemistry and 

Physics, 12, 9025–9040, 2012 op.cit. 12 Transportation Energy Data Book, Edition 33, July 31, 2014 

<http://cta.ornl.gov/data/tedb33/Edition33_Chapter02.pdf> 13 Transportation Energy Data Book, Edition 32, July 31, 2014 

<http://cta.ornl.gov/data/tedb33/Edition33_Chapter02.pdf> 14 http://www.epa.gov/ttnchie1/trends/index.html 15 http://www.epa.gov/otaq/climate/documents/420f11038.pdf 16 See EPA Air Emission Sources, State and County Emissions Summaries <

http://www.epa.gov/air/emissions/where.htm> 17 Aircraft Impact on U.S. Local sand Regional Air Quality, PARTNER Project 15, Final Report , October 

2009 < http://partner.mit.edu/projects/aircraft-impact-us-local-and-regional-air-quality> 18 www.bea.gov/national/xls/gdplev.xls

19http://www.faa.gov/airports/planning_capacity/passenger_allcargo_stats/passenger/media/historicalPasse

ngerTotals.pdf

20 FAA Terminal Area Forecast Summary, Fiscal Years 2012-2040 

http://www.faa.gov/about/office_org/headquarters_offices/apl/aviation_forecasts/taf_reports/media/TAF_s

ummary_report_FY2012.pdf 21 http://www.atag.org/facts-and-figures.html 22 ICAO 2013 Environmental Report, Aviation and Climate Change <http://cfapp.icao.int/EnvironmentalReport-2013/files/assets/basic-html/page33.html> 23 < http://www.faa.gov/nextgen/> 24 http://partner.mit.edu/projects/environmental-cost-benefit-analysis-alternative-jet-fuels 25 Summarizing and Interpreting Aircraft Gaseous and Particulate Emissions Data, ACRP Report 9, 

Whitefield, Philip D., et al, Airport Cooperative Research Program, Transportation Research Board, 

Washington, DC

26 http://www.faa.gov/airports/environmental/ 27 http://www.tandfonline.com/doi/pdf/10.1080/00022470.1979.10470763 28 http://www.trb.org/ACRP/Blurbs.aspx?fields=PublicationType|ACRP

35

 
Aviation Emissions, Impacts & Mitigation: A Primer

29 For example, APEX projects documented in ACRP Report 9 [End Note 32]; ACRP Report 71, Guidance 

for Quantifying the Contribution of Airport Emissions to Local Air Quality; and ACRP Project 02-17, 

Measuring PM Emissions from Aircraft Auxiliary Power Units, Tires, and Brakes. 30 https://aedt.faa.gov 31 http://www.faa.gov/about/office_org/headquarters_offices/apl/research/models/eds/ 32 Lissys Limited, Project Interactive Analysis and Optimization (PIANO), version 5.0.0,

Woodhouse Eves, U.K. 2010, www.piano.aero. 33 http://web.mit.edu/drela/Public/N+3/Final_Report_App.pdf 34 http://suave.stanford.edu; http://nari.arc.nasa.gov/sites/default/files/ALONSO_LEARN.pdf 35 http://partner.mit.edu/projects/development-distributed-approach-system-level-uncertainty-quantification 36 http://partner.mit.edu/projects/analysis-missions-specifications 37 http://www.faa.gov/about/office_org/headquarters_offices/apl/research/models/apmt/ 38 http://www.icao.int/environmental-protection/pages/CAEP.aspx

39 http://www.epa.gov/ttnchie1/trends/index.html 40 See EPA’s Latest Findings on National Air Quality

<http://www.epa.gov/air/airtrends/2007/report/sixprincipalpollutants.pdf> 41 Clean Air Act Amendments of 1990, Title I – Provisions for Attainment and Maintenance of National 

Ambient Air Quality Standards, Section 101(d)(1), November 15, 1990.

42 See Eligible Airports spreadsheet at <http://www.faa.gov/airports/environmental/vale> 43 Aircraft Impacts on Local and Regional Air Quality in the United States, PARTNER Project 15, Final 

Report, October 2009 < http://web.mit.edu/aeroastro/partner/reports/proj15/proj15finalreport.pdf >. 44 http://www.epa.gov/ttnchie1/trends/index.html 45 Surface Air Quality Impacts of Aviation, Barrett, Steven, Laboratory for Aviation and the Environment, 

MIT, presentation to AEC Roadmap 11th Meeting of Primary Contributors, May 14, 2013 46 http://www.faa.gov/about/office_org/headquarters_offices/apl/research/aircraft_technology/cleen 

/reports/media/TAPS_II_Public_Final_Report.pdf 47 Inventory of US Greenhouse Gas Emissions and Sinks, US EPA, April 2014 

http://www.epa.gov/climatechange/Downloads/ghgemissions/US-GHG-Inventory-2014-Main-Text.pdf> 48 http://www.epa.gov/climatechange/emissions/usinventoryreport.html

49 http://cta.ornl.gov/data/chapter2.shtml 50 Aviation and global climate change in the 21st century, Lee, David S., et.al. Atmospheric Environment

Volume 43, Issues 22–23, July 2009, Pages 3520–3537 51 Ibid. 52 http://ascent.aero/

http://partner.mit.edu/projects/aviation-system-global-climate-performance-analysis 53 Brasseur et al., “Impact of Aviation on Climate: FAA’s Aviation Climate Change Research Initiative 

(ACCRI) Phase II”. Submitted, Bulletin of American Meteorological Society (BAMS), October 2014 54 42 USC § 7401 et seq 55 36 FR 8186, Apr 30, 1971 56 40 CFR Parts 50, 51, 52 et al. National Ambient Air Quality Standards for Particulate Matter; Final Rule, 

January 15, 2013 < http://www.gpo.gov/fdsys/pkg/FR-2013-01-15/pdf/2012-30946.pdf> 57 14 CFR Part 34, Fuel Venting and Exhaust Emission Requirements for Turbine Engine Powered 

Airplanes, January 1, 2011

58 NEPA [42 U.S.C. 4321 et seq.] was signed into law on January 1, 1970. Regulations implementing 

NEPA are binding on all federal agencies [40 CFR Parts 1500-15081]

59 For a discussion of General Conformity applicability to airports, see ACRP Report 84, Guidebook for 

Preparing Airport Emissions Inventories for State Implementation Plans, page 12 

<http://onlinepubs.trb.org/onlinepubs/acrp/acrp_rpt_084.pdf> 60 For example PARTNER Project 9 | Measurement of Emissions, Project 12 | Emissions' Atmospheric 

Impacts, Project 15 | Aircraft impact on U.S. local and regional air quality, Project 16 | Investigation of 

aviation emissions air quality impacts, Project 20 | Emissions Characteristics of Alternative Aviation Fuels, 

and Project 29 | Emissions Characteristics of Modern/Future Aviation Sources

36

 
Aviation Emissions, Impacts & Mitigation: A Primer

61 As noted in PARTNER Project 11 | Health Impacts of Aviation Related Air Pollutants, a key finding has 

been “Fine particulate matter dominates the health risks from aviation emissions, with a significant 

contribution from secondarily-formed particles.” 62 Health Risks of Particulate Matter From Long-Range Transboundary Air Pollution, World Health 

Organization, Joint WHO/Convention Task Force on the Health Aspects of Air Pollution, 2006. < 

http://www.euro.who.int/__data/assets/pdf_file/0006/78657/E88189.pdf> 63 Ultrafine Particle Health Effects, John R. Froines, Ph.D., Southern California Particle Center, <

http://www.aqmd.gov/docs/default-source/technology-research/ultrafine-particles-conference/preconference_2_froines.pdf?sfvrsn=2

64 http://pubs.acs.org/doi/full/10.1021/es101325r 65 36 FR 8186, Apr 30, 1971 66 40 CFR Parts 50, 51, 52 et al. National Ambient Air Quality Standards for Particulate Matter; Final Rule, 

January 15, 2013 < http://www.gpo.gov/fdsys/pkg/FR-2013-01-15/pdf/2012-30946.pdf> 67 International Civil Aviation Organization, International Standards and Recommended Practices, 

Environmental Protection, Annex 16 to the Convention on International Civil Aviation, Volume II, Aircraft 

Engine Emissions

68 Smoke number is a dimensionless term that quantifies smoke emissions, that is, carbonaceous materials 

in exhaust emissions which obscure the transmission of light.

69 ASTM International D 1655-04a, Standard Specification for Aviation Turbine Fuels 70 http://www.crcao.org/reports/recentstudies2012/AV-01-

10%20Sulfur%20Study/CRCFinalReportProjectAV-1-10November2012.pdf 71 Environmental Protection Agency, Office of Transportation and Air Quality, Final Regulatory Analysis: 

Control of Emissions from Non-Road Diesel Engines, EPA420-R-04-007, May 2004. 72 Based on emissions factors for diesel, gasoline, and natural gas powered equipment from EPA’s Nonroad 

Model, which is the basis of GSE emissions computations in AEDT.

73 PM is emitted during electricity generation at the power plant, however, utility power production is well 

controlled compared to internal combustion engines and the net result is fewer PM emissions. 74 40 CFR Part 1039 – Control of Emissions from New and In-Use Nonroad Compression-Ignition Engines 

< http://www.ecfr.gov/cgi-bin/text-idx?tpl=/ecfrbrowse/Title40/40cfr1039_main_02.tpl 75 See for example Airport Emission Inventory Denver International Airport 

<http://www.colorado.gov/airquality/documents/deno308/diaDenver_SIPemissionsinventory_finaldraft.pdf

>, Greenhouse Gas Emissions Inventory Philadelphia International Airport 

<http://www.phl.org/AboutPHL/Environmentalinitiatives/SustainabilityInitiatives/Documents/GHGinvento

ryFinalSH.pdf> 76 http://www.epa.gov/airtrends/aqtrnd04/pmreport03/pmunderstand_2405.pdf 77 See for example ACRP Project 02-42, Understanding Air Quality and Public Health Studies Related to 

Airports <http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3247>. Also activities 

underway in PARTNER Project 11, Health Impacts of Aviation Related Air Pollutants 

<http://partner.mit.edu/projects/health-impacts-aviation-related-air-pollutants>. 78 International Civil Aviation Organization, International Standards and Recommended Practices, Annex 

16 to the Convention on International Civil Aviation, Volume II Aircraft Engine Emissions, Third Edition 

2008.

79 40 CFR 87.89, Compliance with Smoke Emission Standards, July 1, 2012 80 Federal Register 31 December 2012, pages 76842 -76854,

< https://www.federalregister.gov/articles/2012/12/31/2012-31109/exhaust-emissions-standards-for-newaircraft-gas-turbine-engines-and-identification-plate-for> 81 40 CFR Parts 87 and 1068, Control of Air Pollution From Aircraft and Aircraft Engines; Emission 

Standards and Test Procedures, Federal Register/Vol. 77, No. 117/Monday, June 18, 2012/Rules and 

Regulations, < http://www.gpo.gov/fdsys/pkg/FR-2012-06-18/pdf/2012-13828.pdf> 82 See for example Current and Future Nitrogen Oxides (NOx) Emissions by Freight Transportation Mode: 

2002, 2010, 2020, <

http://ops.fhwa.dot.gov/freight/freight_analysis/nat_freight_stats/docs/07factsfigures/table5_13.htm> US 

DOT, Federal Highway Administration; also, van Velthoven, Peter, The impact of emissions from shipping, 

aviation and road traffic on atmospheric composition and climate, <

37

 
Aviation Emissions, Impacts & Mitigation: A Primer

http://www.knmi.nl/research/biennial/05-06_Transport.pdf>, Royal Netherlands Meteorological Institute, 

Ministry of Infrastructure and the Environment, 2009.

83 http://www.boeing.com/boeing/commercial/787family/background.page? 84 Boeing Revises 737 Max Fuel-Burn Advantage Upward <http://www.ainonline.com/aviation-news/ainair-transport-perspective/2013-11-04/boeing-revises-737-max-fuel-burn-advantage-upward> 85 Air Travel And Efficiency: How U.S. Airports Are Saving Energy < http://www.ase.org/resources/airtravel-and-efficiency-how-us-airports-are-saving-energy>. See also for example ACRP Project 02-16,

Handbook for Considering Practical Greenhouse Gas Emission Reduction Strategies for Airports <

http://onlinepubs.trb.org/onlinepubs/acrp/acrp_rpt_078.pdf> and ACRP Project 02-06, Guidebook on 

Preparing Airport Greenhouse Gas Emissions Inventories.

< http://onlinepubs.trb.org/onlinepubs/acrp/acrp_rpt_011.pdf>. 86 FAA Modernization and Reform Act of 2012 <

http://www.faa.gov/regulations_policies/reauthorization/media/PLAW-112publ95[1].pdf> 87 Aviation Climate Change Research Initiative (ACCRI) Phase II Report, Brasseur, Guy P., et al, US 

Federal Aviation Administration, Washington, DC, April 18, 2013. Also, planned climate change research 

projects Impact of Cruise Altitude Emissions on Surface Air Quality – Characterizing the Uncertainties in 

Surface Air Quality and 2050 Alternative Fuels Scenarios. 88 http://www.faa.gov/airports/environmental/vale/

89 http://www.faa.gov/airports/environmental/vale/media/valeGrantSummary.pdf

90 http://www.faa.gov/airports/environmental/zero_emissions_vehicles/

91 2011 The Future of Aviation Advisory Committee (FAAC) Final Report, 

http://www.dot.gov/sites/dot.dev/files/docs/faac-final-report-for-web.pdf

92 http://www.astm.org/Standards/D7566.htm

93 http://www.greenaironline.com/news.php?viewStory=1974

94 http://www.caafi.org

95 https://www.faa.gov/about/initiatives/avgas/archive/ 96 https://www.faa.gov/about/initiatives/avgas/archive/ 97 http://partner.mit.edu/about/collaborating-universities

98 http://web.mit.edu/aeroastro/partner/about/board.html 99 Aviation Environmental and Energy Policy Statement, Department of Transportation, Federal Aviation 

Administration, July 2012 <

http://www.faa.gov/about/office_org/headquarters_offices/apl/environ_policy_guidance/policy/media/FAA

_EE_Policy_Statement.pdf> 100 PL112–9 FEB. 14, 2012 < http://www.faa.gov/regulations_policies/reauthorization/media/PLAW112publ95[1].pdf> 101 Independent Review of FAA’s Energy-Related and Environment-Related Research Programs, June 

2013. 

<https://www.faa.gov/about/office_org/headquarters_offices/agi/reports/media/FAA_Report_to_Congress_

on_Energy_and_Environment_Research_Programs.pdf> 102 Aviation Greenhouse Gas Emission Reduction Plan – DOT/FAA June 2012 <

http://www.faa.gov/about/office_org/headquarters_offices/apl/environ_policy_guidance/policy/media/Avia

tion_Greenhouse_Gas_Emissions_Reduction_Plan.pdf

38