Regulatory Announcement

EPA Takes First Steps to Address GHG 

Emissions from Aircraft Engines 

The EPA Administrator is proposing to find that greenhouse gas 

(GHG) emissions from certain classes of engines used in aircraft 

contribute to the air pollution that causes climate change and endangers 

public health and welfare under section 231(a) of the Clean Air Act 

(CAA or the Act). The EPA is not at this time proposing aircraft 

engine GHG emission standards. 

The EPA is also issuing an Advance Notice of Proposed Rulemaking 

that provides information on the process for setting an international 

CO2

 emissions standard for aircraft at the International Civil Aviation 

Organization (ICAO), and describes and seeks input on the potential 

use of section 231 of the Clean Air Act to adopt and implement the 

corresponding international aircraft engine CO2

 emissions standard 

domestically. 

The Clean Air Act and Aircraft Regulation 

The EPA has been engaged in reducing harmful air pollution from aircraft engines 

since 1973. Section 231 of the Clean Air Act directs the EPA to issue standards 

addressing aircraft engine pollutant emissions, if in the Administrator’s judgment 

they cause or contribute to air pollution which may reasonably be anticipated to 

endanger public health or welfare. Under the Clean Air Act, the EPA consults with 

the Federal Aviation Administration as we develop aircraft engine emission standards, ensuring that any standards set do not adversely affect safety or increase noise. 

Section 232 of the Clean Air Act then requires that the FAA ensure compliance 

with the emissions standards set by the EPA. 

The EPA and the FAA have traditionally worked within the International Civil 

Aviation Organization (ICAO), a specialized body of the United Nations focused on 

aviation and comprised of 191 member states, to first establish international emission 

standards. Subsequently, the EPA has initiated rulemakings under Clean Air Act 

section 231 to establish domestic standards equivalent to ICAO’s standards. Aircraft 

Office of Transportation and Air Quality 

EPA-420-F-15-023 

June 2015 
Regulatory Announcement

engine standards for other exhaust pollutants including hydrocarbons, oxides of nitrogen, carbon 

monoxide, and smoke already exist and were developed in accordance with this international 

process. The proposed GHG cause and contribution findings for aircraft engines are an initial 

step toward potentially aligning future international and U.S. standards for CO2

 emissions from 

aircraft engines. 

Background 

In 2009 the EPA issued findings under Clean Air Act section 202 that GHG emissions from 

motor vehicles cause or contribute to the air pollution that causes climate change endangering 

public health and welfare. Subsequent to this finding, EPA adopted GHG emission standards for 

motor vehicles under section 202 of the Act. We are not reopening or revising our prior finding 

under CAA section 202(a) in this proposed action. 

To address GHG emissions from aircraft, EPA would first issue a separate and final finding under 

section 231 of the Act concluding that GHGs from aircraft engines contribute to the pollution 

that causes climate change thus endangering public health and welfare. In this proposed action, 

the EPA relies upon the extensive scientific and technical evidence in the record supporting the 

2009 finding, and builds on it with more recent major scientific assessments. Since 2009, the 

science on climate change has strengthened lending further support to the judgment that GHGs 

in the atmosphere endanger public health and welfare for purposes of section 231. 

The Administrator’s proposed findings come in response to a citizen petition submitted by 

Friends of the Earth, Oceana, the Center for Biological Diversity, and Earthjustice (Petitioners) 

requesting that the EPA issue a GHG endangerment finding and standards under section 231(a) 

(2)(A) of the Act for GHG emissions from aircraft engines. Further, the EPA anticipates that 

ICAO will adopt a final international aircraft CO2

 emissions standard in February 2016. This 

proposal and any final GHG endangerment and cause or contribute findings for aircraft engines 

are part of preparing for a possible subsequent domestic rulemaking process to adopt the corresponding international aircraft CO2

 emissions standard under CAA section 231. 

Aircraft GHG Emissions 

The U.S. transportation sector is a significant contributor to total U.S. and global anthropogenic GHG emissions. Aircraft remain the single largest GHG-emitting transportation source not 

yet subject to GHG standards in the U.S. 

U.S. aircraft emit: 

•	 11 percent of GHG emissions from the transportation sector in the U.S. 

•	 3 percent of total U.S. GHG emissions. 

•	 29 percent of GHG emissions from all aircraft globally. 

•	 0.5 percent of total global GHG emissions. 

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Regulatory Announcement

Proposed Endangerment and Cause and Contribute Findings 

The EPA Administrator is proposing to find that GHG emissions from certain classes of engines 

used primarily in commercial aircraft contribute to the air pollution that causes climate change 

and endangers public health and welfare. Specifically, she proposes to find that GHG concentrations in the atmosphere endanger the public health and welfare of current and future generations within the meaning of section 231(a) of the Clean Air Act. She proposes to make this 

finding specifically with respect to the same six well-mixed GHGs -- carbon dioxide, methane, 

nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride -- that together 

were defined as the relevant air pollution in the 2009 Endangerment Finding under section 

202(a) of the Clean Air Act. The Administrator is also proposing to find that GHG pollutant 

emissions from certain classes of engines used in aircraft are contributing to this mix of GHGs in 

the atmosphere. 

Proposed Scope of Covered Aircraft Engines 

The Administrator proposes to find that GHG emissions from engines used in U.S. subsonic jet 

aircraft with a maximum takeoff mass (MTOM) greater than 5,700 kilograms and in subsonic 

propeller driven (e.g., turboprop) aircraft with a MTOM greater than 8,618 kilograms, contribute to the GHG air pollution that endangers public health and welfare. Examples of covered 

aircraft would include smaller jet aircraft such as the Cessna Citation CJ2+ and the Embraer 

E170, up to and including the largest jet aircraft - the Airbus A380 and the Boeing 747. Other 

examples of covered aircraft would include larger turboprop aircraft, such as the ATR 72 and the 

Bombardier Q400. 

The Administrator is not at this time proposing a contribution finding for GHG emissions from 

engines used in military aircraft or smaller aircraft such as smaller turboprops, smaller jet aircraft, 

piston-engine aircraft, and helicopters. 

Advance Notice of Proposed Rulemaking (ANPR) 

Over the past five years, the International Civil Aviation Organization (ICAO), a specialized 

body of the United Nations with 191 member states, has been working with the aviation industry and environmental groups to develop a coordinated, international CO2

 emissions standard 

for aircraft. EPA and the Federal Aviation Administration (FAA) represent the United States 

on ICAO’s Committee on Aviation Environmental Protection (CAEP), and are working to 

ensure that CAEP develops an international standard that achieves meaningful CO2 emissions 

reductions through policies that are equitable across national boundaries. This international 

standard is expected to be adopted in early 2016. 

Today’s notice is an initial step in the process for EPA to adopt CO2

 standards promulgated by 

ICAO in the future. It provides the public and stakeholders with information on the ICAO 

standard-setting process and requests input on the setting of these standards. The EPA is seeking 

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Regulatory Announcement

 

comments from all interested parties, including small businesses, on a variety of issues related to 

setting CO2

 standards for aircraft, including: 

•	 The appropriate effective dates for the potential international CO2

 standard 

•	 The appropriate stringency levels for the CO2

 standard 

•	 Whether international standards should apply to new in-production aircraft as well as 

new aircraft types 

Participation 

We welcome your comments on these proposed endangerment and contribution findings and 

ANPR. Comments will be accepted for 60 days beginning when this proposal is published 

in the Federal Register. All comments should be identified by Docket ID No. EPA-HQOAR-2014-0828 and submitted by one of the following methods: 

Internet: www.regulations.gov 


E-mail: A-and-R-Docket@epa.gov
 

Mail:
 

Environmental Protection Agency 

Air and Radiation Docket and Information Center (6102T) 

1200 Pennsylvania Avenue NW 

Washington, DC 20460 

Hand Delivery: 

EPA West building
 

EPA Docket Center (Room 3340)
 

1301 Constitution Avenue NW
 

Washington, DC
 

You should consult the Federal Register notice for this proposal for more information about 

how to submit comments, when the comment period will close, and about where and if a public 

hearing will be held. 

For More Information 

You can access the proposal and ANPR on EPA’s Office of Transportation and Air Quality 

(OTAQ) Website: 

www.epa.gov/otaq/aviation.htm 

For more information on this proposal and ANPR, please contact the U.S. Environmental 

Protection Agency, Office of Transportation and Air Quality at: 

E-mail: otaq@epa.gov 

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