LONDON, England (CNN) -- Police arrested an American Airlines pilot who failed a Breathalyzer test at London's Heathrow Airport on Wednesday, the airline and police said Thursday.
The pilot was due to fly a London-to-Chicago, Illinois, route leaving Heathrow at 10:15 a.m. He was replaced, and the flight departed at 11:30 a.m., the airline said.
It declined to name the pilot.
London's Metropolitan Police said he was a 57-year-old who was arrested 20 minutes before the plane was due to take off.
He took a blood test, the results of which are not yet available, the American Airlines' pilots' union said.
Arrests of drunken pilots are "quite infrequent," said a police spokesman who declined to be named, in line with police policy. "They are not everyday occurrences."
The police declined to say how far over the limit the pilot was.
He was released on bail to face a possible court appearance in July.
"Alcohol testing is part of the Federal Aviation Administration's random drug testing program, and can occur prior to or after any flight assignment," said Scott Shankland, a spokesman for the pilots' union. "However, the testing is random and rare. Definitely not routine."
Since 1999, 22 pilots have appealed to the National Transportation Safety Board in the United States after the Federal Aviation Administration took action against them for alcohol consumption, the board said. All the appeals were rejected.
Seventeen of those suspended were commercial pilots; the other five were private, the safety board said.
The aviation agency did not immediately respond to a question about how many pilots had been suspended for alcohol consumption. Britain's Civil Aviation Authority said it does not keep such records.
CNN's Mike Ahlers in Washington contributed to this report.