LONDON — The crew of a Japan Airlines flight was traveling by bus to Heathrow Airport here when the bus driver had a suspicion that there was something wrong with the co-pilot.

He could smell it on his breath.

After the bus driver alerted the authorities, the co-pilot, Katsutoshi Jitsukawa, 42, was arrested at Heathrow — 50 minutes before his flight to Tokyo. A breath test showed that he was almost 10 times over Britain’s legal alcohol limit for pilots.

Mr. Jitsukawa admitted that he had consumed two bottles of wine and five cans of beer hours before he was to help pilot Flight JL044 last Wednesday, the authorities said.

At the Uxbridge Magistrates Court on Thursday, the co-pilot pleaded guilty to exceeding the legal alcohol limit, a spokesman for the Metropolitan Police said. He was detained until his sentencing on Nov. 29.