Updated February 8, 2022
Aviation, Air Pollution, and Climate Change
Some Members of Congress have expressed interest in
impact could be from two to four times that of its past CO2
addressing air pollution emissions, greenhouse gas (GHG)
emissions alone.
emissions, and the climate change effects from domestic
and international aviation. Proposed legislation in the 117th
Aside from GHG emissions, aircraft engines emit a number
Congress would provide for sustainable fuel mandates,
of criteria—or common—pollutants, including nitrogen
incentives for airport efficiency improvements, and GHG
oxides, carbon monoxide, oxides of sulfur, unburned or
emission targets, among other requirements.
partially combusted hydrocarbons (also known as volatile
organic compounds [VOCs]), particulates, and other trace
Emissions from Aircraft
compounds. A subset of the VOCs and particulates are
The U.S. Environmental Protection Agency (EPA)
considered hazardous air pollutants.
estimates that transportation—including passenger cars and
light trucks, heavy-duty trucks, buses, trains, ships, and
Emission Reduction Strategies
aircraft—accounted for 35% of carbon dioxide (CO2, the
In an effort to reduce emissions from the aviation sector,
principal GHG) emissions in 2018. While CO2 emissions
the U.S. government, other nations, and international
from passenger cars and light trucks exceed those from
organizations have worked together with the aviation
aircraft in the United States, CO2 emissions from aviation
industry toward improving technologies, increasing the
are currently experiencing a faster rate of growth. All
efficient use of aircraft and airport infrastructure, adopting
aircraft, including military, commercial, and privately
appropriate economic incentives, and setting standards.
chartered, accounted for 13% of the U.S. transportation
sector’s CO
Aircraft Emission Standards: Domestic Process
2 emissions and 5% of all U.S. CO2 emissions in
2018. Commercial aircraft, including those operated by
In the United States, in accordance with Clean Air Act
passenger and all-cargo airlines, accounted for 11% of
(CAA) Section 231 (42 U.S.C. §7571), EPA sets emission
transportation sector and 4% of all emissions. These
levels for specified pollutants, as promulgated in 40 C.F.R.
estimates include emissions from U.S. domestic flights and
Part 87, “Control of Air Pollution from Aircraft and
emissions from international flights departing the United
Aircraft Engines.” EPA sets standards for Federal Aviation
States, referred to as “international bunkering.”
Administration (FAA)-certified aircraft according to the
amount of thrust generated by their engines. Aircraft
In the United States, aggregate CO2 emissions from aircraft
emission standards currently exist for fuel venting, and
have fluctuated due to changes in technology, the economy,
engine hydrocarbons, carbon monoxide, and nitrogen
travel frequency, and military activity, among other
oxides. In 2021, EPA promulgated standards for CO2
reasons. However, since the global financial crisis in 2009,
emissions from aircraft engines. In 2022, EPA proposed
aggregate CO2 emissions from all aircraft types have grown
standards for particulate emissions from certain classes of
steadily, increasing by almost 22% between 2009 and 2018.
engines used by civil subsonic jet aircraft (87 Federal
This increase makes aircraft one of the faster-growing
Register 2735, January 19, 2022), and announced plans to
sources of CO2 emissions in the U.S. transportation sector
evaluate lead pollution from gasoline-powered, piston-
over the past decade. This trend is likely to be affected, at
engine aircraft (with a proposed endangerment finding
least temporarily, by reduced air travel in 2020 and 2021
scheduled for release in 2022).
due to Coronavirus Disease 2019 (COVID-19).
The standard-setting language under CAA Section 231 is
The effects of aircraft emissions on the atmosphere are
similar to the statutory language for other mobile sources in
complex, reflecting differing altitudes, geography, time
the CAA (e.g., cars, trucks, buses). However, compared to
horizons, and environmental conditions. Research has
other mobile sources, EPA must meet additional
shown that in addition to CO2 emissions, other factors
requirements in setting emission standards for aircraft and
increase the climate change impacts of aviation. These
aircraft engines: (1) the EPA Administrator must consult
factors include the contribution of aircraft emissions to
with the Administrator of the FAA and the Secretary of the
ozone production; the formation of water condensation
U.S. Department of Transportation (DOT) in developing
trails and cirrus clouds; the emission of various gases and
emission standards; (2) the EPA Administrator cannot
particles, including water vapor, nitrous oxides, sulfates,
change standards if doing so would “significantly increase
and particulates from jet fuel combustion; and the high
noise and adversely affect safety”; and (3) the President
altitude location of the bulk of these emissions. In
may disapprove any such standards if the DOT Secretary
examining the warming and cooling influences of these
finds that they “would create a hazard to aircraft safety.”
factors, the United Nations’ Intergovernmental Panel on
CAA Section 232 requires the FAA to enforce the standards
Climate Change estimated aviation’s total climate change
at the time an engine is certified for emissions under 14
C.F.R. Part 34, “Fuel Venting and Exhaust Emission
https://crsreports.congress.gov
Aviation, Air Pollution, and Climate Change
Requirements for Turbine Engine Powered Airplanes.”
cover U.S. subsonic jet and propeller-driven aircraft above
Since compliance with the federal standards is determined
certain takeoff weights.
at engine certification, there are no operational emissions
regulations for aircraft.
Upon EPA’s promulgation of the rule, CAA Section 232
requires the FAA to issue regulations to enforce the
Aircraft Emission Standards: International Process
standards and apply such standards when certifying the
Due to the global nature of the aircraft manufacturing
engines of U.S. aircraft manufacturers. EPA stated that the
industry and its customer base, EPA has generally regulated
standards would make domestically manufactured aircraft
emissions from aircraft only after the United States has
engines competitive in the global marketplace; however, the
negotiated an international agreement through the
agency also acknowledged that the rule likely would not
International Civil Aviation Organization (ICAO). ICAO is
spur any emissions reductions from U.S. aircraft
a United Nations specialized agency established in 1944 to
manufacturers beyond their current trends.
manage the administration and governance of the
Market-Based Mechanisms
Convention on International Civil Aviation (the Chicago
In October 2016, ICAO also agreed on a framework for
Convention). ICAO has 193 member states, including the
offsetting future carbon emissions from aviation—referred
United States. ICAO addresses civil aviation (i.e., all
to as the Market-Based Mechanism, or MBM. ICAO
nonmilitary, private, and commercial aviation).
member states agreed to implement a “Carbon Offsetting
and Reduction Scheme for International Aviation
ICAO’s activities regarding environmental protection focus
(CORSIA) to address any annual increase in total CO
on issues that could benefit most from a worldwide
2
emissions from international civil aviation (i.e. civil
coordinated approach—for example, aircraft noise and
aviation flights that depart in one country and arrive in a
engine emissions. After member states agree to a negotiated
different country) above the 2020 levels, taking into
set of international standards, they implement these
account special circumstances and respective capabilities.”
standards through their own domestic laws and regulatory
CORSIA relies on the use of emissions units from carbon
processes. ICAO has no direct regulatory or enforcement
markets to offset the amount of CO
authority. Typically, ICAO’s international standards for
2 emissions that cannot
be reduced through the use of sustainable aviation fuels or
pollutants from aircraft, unlike EPA’s regulation of the
technological and operational improvements. CORSIA
same pollutants from on-road vehicles, have consistently
began in 2021. Compliance was to be measured against a
avoided technology-forcing requirements. For example, the
baseline of CO
most recent ICAO standards for nitrogen oxides essentially
2 emissions defined as the average from all
international civil aviation in 2019 and 2020. However, due
ratified what the principal aircraft manufacturers had
to the effects of the COVID-19 pandemic on international
already achieved.
air travel in 2020, the ICAO adopted a baseline based solely
Greenhouse Gas Emission Reduction Strategies
on 2019 emissions for a three-year pilot phase.
CO2 Emission Standards
Participation in CORSIA is voluntary for the next decade.
Since 2010, ICAO has negotiated with the aviation industry
The U.S. aviation industry agreed to participate during
and selected stakeholders to develop international CO2
ICAO negotiations. To fulfill the U.S. commitments under
emission standards for aircraft engines. A delegation of
the Chicago Convention with respect to the MBM, FAA
EPA and FAA representatives have participated in ICAO’s
implemented the CORSIA Monitoring, Reporting, and
process. In March 2017, ICAO adopted international CO2
Verification Program in 2019 (84 Federal Register 9412,
standards for commercial aircraft engines to begin in 2020.
March 14, 2019). Whether, and if so when, ICAO member
The ICAO standards represent the world’s first global
states adopt CORSIA as a standard is under negotiation. At
design certification measure governing CO2 emissions for
that point, one question would be whether EPA’s authority
any industry sector. The standards apply to newly
under CAA Section 231 to “issue proposed emission
developed civil aircraft designs phased-in between January
standards” is broad enough to include setting a trading
1, 2020, and January 1, 2023, and to in-production aircraft
scheme to comply with CORSIA’s requirements.
after January 1, 2028. They do not apply to already-
Other Reduction Strategies
manufactured aircraft that are currently in use. CO2
Beyond federal and international CO
emissions targets vary by aircraft type and are set as a
2 emission standards
for aircraft engines, other policy options are available to
function of the aircraft’s maximum takeoff weight.
reduce GHGs from the aviation sector. These include (1)
taxes on fuel or its carbon content; (2) mandates to use
In accordance with the ICAO negotiations and the CAA,
sustainable aviation fuels or fuel alternatives; (3) incentives
EPA issued a finding that GHG emissions (including CO2
to modernize air traffic control systems (see CRS In Focus
emissions) from civil aircraft contribute to the pollution that
IF11420, Aircraft Noise and Air Traffic Control
causes climate change and endangers U.S. public health and
Modernization); and (4) ground-based measures aimed at
welfare (81 Federal Register 54422, August 15, 2016).
EPA’
reducing GHG emissions from nonaircraft operations at
s endangerment finding, under Section 231 of the
airports. FAA and EPA administer several initiatives in
CAA, laid the necessary foundation for adoption and
operations and research, and collaborate at the national and
implementation of CO2 standards for U.S. aircraft, in
international levels, in support of many of these policies.
consultation with FAA. On January 11, 2021, EPA
promulgated GHG emission standards for aircraft engines
Richard K. Lattanzio, Specialist in Environmental Policy
equivalent to the CO2 standards adopted by the ICAO (86
Federal Register 2136, January 11, 2021). The standards
IF11696
https://crsreports.congress.gov
Aviation, Air Pollution, and Climate Change
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
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https://crsreports.congress.gov | IF11696 · VERSION 4 · UPDATED