(Recasts first paragraph; adds comment from ICAO, details on cost of ICAO standard)
By Valerie Volcovici
WASHINGTON, July 25 (Reuters) - The U.S. Environmental Protection Agency on Monday paved the way for new curbs on emissions from passenger jets by ruling that greenhouse gases from airplanes endanger public health.
The finding, which requires the EPA to regulate greenhouse gas emissions from aircraft under the federal Clean Air Act, removes a hurdle to implementing internationally agreed rules on airliner pollution in the United States, the world's biggest domestic travel market.
"Addressing pollution from aircraft is an important element of U.S. efforts to address climate change," EPA Acting Assistant Administrator for Air and Radiation Janet McCabe said in a statement.
U.S. aircraft are the third-biggest source of greenhouse gas emissions from the domestic transportation sector and are projected to rise without future curbs, McCabe said.
The endangerment finding triggers the start of an EPA rule- making process either to adopt the emission standard developed by the U.N. International Civil Aviation Organization or develop one that is "at least as stringent."
In February, after six years of talks, the ICAO agreed on a global standard aimed at makers of small and large planes, including Airbus Group SE and Boeing Co, that will apply to all new aircraft models launched after 2020.
The standard awaits approval by ICAO's governing council in Montreal this fall before being adopted in March 2017.
The ICAO emissions standard will mean that approximately 40 percent of current aircraft designs will need to be improved or will end production by 2028, said Anthony Philbin, a spokesman for ICAO.
The latest planes from companies such as Boeing and Airbus - which cost tens of billions of dollars to develop - will meet the new emissions standards, and environmental groups argue that ICAO merely ratified what manufacturers were already doing.
Airbus, Boeing and their engine manufacturers invested tens of billions of dollars in new technology to save fuel, which also cuts carbon emissions, during the last decade of higher oil prices.
Concerns about the industry and economic impact made negotiations on a standard difficult. U.S. officials had pushed for a quicker phase-out of less-efficient planes than their E.U. counterparts.
ICCT, an environmental research group, said the EPA rule-making process triggered by Monday's finding offers the United States the opportunity to create a more stringent standard that will make use of "cost-effective emerging technologies."
ICCT's Dan Rutherford said fuel burn of new aircraft designs can be reduced by 25 percent by 2024, three times what is required by the proposed ICAO standard.
The Obama administration has tackled emissions from power plants and automobiles but had yet to regulate the U.S. commercial aviation sector.
The next U.S. administration, which will take office next January, will largely oversee the aviation rule-making process.
Aviation and shipping account for around 5 percent of global emissions, a share expected to grow to a third of all emissions by 2050 if left unchecked, according to European Commission data. (Reporting by Valerie Volcovici and Timothy Gardner; Editing by Dan Grebler)
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