Several states and environmental groups petitioned the U.S. Environmental Protection Agency seeking regulation of greenhouse gas emissions from the aviation industry. European nations have also sought to impose such limits. As the NYT reports, the industry already has substantial incentive to reduce its fuel use.

The petitioners suggested several steps to curb emissions, including the use of lighter and more efficient planes and the adoption of flight techniques that require less fuel. The aviation industry is already pursuing some such measures, because it is desperate to reduce its fuel costs. And the less fuel burned, the less greenhouse gas results.

"We have been as green as green can be," said David Castelveter, a spokesman for the Air Transport Association, the trade group of the big carriers.

Mr. Castelveter said that his industry was not troubled by the E.P.A.'s looking into the issue and that efficiency had risen sharply over the last seven years. Among other steps, the airlines are matching passenger load to the number of seats, with the result that they are often flying smaller planes.

The petitions also suggest using alternative jet fuels. That idea is in its infancy, but Japanese researchers are pursuing fuels that can be made from plants instead of oil.

The article further notes that some ways of increasing airplane fuel efficiency can increase airport capacity, potentially increasing the overall amount of air travel and aggregate emissions.

For more on the issue, and links to the petitions, see here.