Having gone after power plants, cars, and trucks, the Environmental Protection Agency has turned its sights to another source of greenhouse-gas emissions: airplanes.

The EPA on Wednesday said that greenhouse-gas emissions from the airline industry pose a threat to public health, and the agency opened the door to regulating the industry for the first time.

According to the agency's draft "endangerment finding," the emissions from commercial aircraft contribute to climate change, "endangering the health and welfare of Americans." That opens the door for further action, similar to the regulations EPA has imposed on light-duty cars and trucks, although the agency did not propose such action on Wednesday. The finding also paves the way for the U.S. to adopt and enforce international standards on airline emissions.

Airline emissions contribute about 2 percent of the world's greenhouse-gas emissions. U.S. airlines account for about 3 percent of the country's total greenhouse-gas emissions and 11 percent of the country's emissions from the transportation sector. According to the EPA, U.S. aircraft make up 29 percent of the world's airline emissions.

But thanks to growth in the industry at home and abroad—American airlines are expecting record numbers this year—those numbers are expected to grow. The International Council on Clean Transportation says emissions are rising at a rate of 3 to 4 percent a year, with the potential to quadruple by 2050.

The regulations come amid international action on airline emissions from the International Civil Aviation Organization (ICAO), which has been slowly looking at a global emissions strategy. ICAO is scheduled to release its own CO2 standard for aircraft in February 2016 for public comment, with adoption later that year.

An airline industry official told Reuters that ICAO is weighing either a market-based system that would allow airlines to buy carbon offsets to balance emissions, or a global emission standard for aircraft.

Given the global nature of the industry, airlines say they'd like to see one international standard rather than individual standards for each country.

They'd like to avoid, for example, further action by the European Union, which put a fee on greenhouse-gas emissions for flights in and out of Europe. That system faced opposition from companies and countries who bristled at paying into a scheme they didn't participate in (the U.S. passed a law exempting domestic airlines), and the E.U. backtracked to confine the regulations only to flights within the European Economic Area until ICAO takes further action.

In a statement, EPA said it was working with ICAO and that the agency's action would "lay the necessary foundation for the development and implementation of a domestic aircraft standard, in accordance with U.S. law and the ICAO process."

Environmentalists say that ICAO is moving far too slowly to check airline emissions and that the standards being considered by the body just aren't sufficient.

Vera Pardee, a senior attorney at the Center for Biological Diversity, said her group is "especially concerned" about ICAO's laxity, especially if it produces a rumored standard that would apply only to newly designed aircraft. That, Pardee said, could leave ICAO regulating as little as 5 percent of the fleet in a few decades, since aircraft have a life span of 25-30 years.

CBD, along with Friends of the Earth and Earthjustice, petitioned EPA for action on aviation last spring, saying that the agency had been required under a 2010 court order to crack down. That action prompted the rulemaking, although greens say they'd like to see EPA move quickly to ensure the regulations take effect soon.

"President Obama is taking an important step on climate once again by finding that carbon pollution from airplanes poses the same danger to our climate as carbon pollution from other sources," said Sierra Club attorney Joanne Spalding. "This finding paves the way for action next year to create safeguards that will result in more efficient airplanes which pollute less while saving airlines and air travelers money on fuel costs."

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