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 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 man 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.american airlines

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.

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.

The aviation agency did not immediately respond to a CNN question about how many pilots had been suspended for alcohol consumption. Britain's Civil Aviation Authority said it does not keep such records.