Nick Ut, Associated Press
American Airlines flight #AA135 from London crosses the Waxing Gibbous moon as it approaches Los Angeles International Airport in Whittier, Monday, March 30, 2015.

WASHINGTON — The government is proposing to regulate aircraft emissions in much the same way as power plants, saying they are a threat to human health because they contain pollutants that help cause global warming and therefore should be regulated.

The Environmental Protection Agency announcement Wednesday clears the way for possible U.S. adoption of international emissions standards, which are expected to be released next year.

U.S. regulations wouldn't apply to small piston-engine planes or military aircraft.

The International Civil Aviation Organization, a U.N. agency, has been working for several years on developing global aircraft emissions standards for the first time.

While negotiations on the standards are still underway, environmentalists say the standards aren't expected to go into effect until 2020 or afterward — possibly as late as 2025.