A United Airlines pilot who failed a breath test shortly before he was due to take off has been charged with having too much alcohol in his system, British police said.

Erwin Vermont Washington, 51, is the third U.S. pilot in 13 months to be arrested for being over the strict alcohol limits imposed on airline staff.

Washington was arrested after officers were called to United Airlines Flight 949, which was already full of passengers and due to leave London's Heathrow Airport just after noon on Monday.

A spokeswoman for BAA Airports Ltd., Heathrow's operator, said late Tuesday the pilot had been reported to authorities by another member of United's staff. She spoke on condition of anonymity, saying it was company policy.

It was not immediately clear how much alcohol Washington was accused of having consumed. Under British law, pilots are forbidden from having any more than 20 micrograms of alcohol for each 100 milliliters of blood in their system, or .02 percent. For most average-sized men, that is the equivalent of having just had about half a glass of regular strength beer.

Scotland Yard said that Washington, who has been released on bail, would have to appear at a court in northwest London on Nov. 20. If convicted, he faces up to two years in prison, a fine, or both.

United Airlines, a subsidiary of Chicago-based UAL Corp., said the pilot had been removed from service pending an investigation.

Monday's incident echoes the arrest in May of an American Airlines pilot _ also at Heathrow and also scheduled to fly a plane to Chicago _ after he failed a breath test. In October 2008, another United Airlines pilot was arrested by police for being over the alcohol limit.

Union leaders say pilots are under increased scrutiny by security agents and passengers because of high-profile cases involving drunk pilots.