JAL said from now on it will involve airport staff in alcohol checks rather than getting pilots to test each other.
The driver of a Heathrow Airport crew bus noticed the smell of alcohol on the co-pilot's breath and reported it to police, according to JAL.
Japan Airlines co-pilot Katsutoshi Jitsukawa was arrested Sunday after failing a breath test shortly before a London to Tokyo flight and pleaded guilty in court today to being nearly 10 times over the legal limit for alcohol.
JAL withheld the co-pilot's identify, but London's Metropolitan Police identified him as 42-year-old Katsutoshi Jitsukawa.
Jitsukawa said he had drunk about two bottles of wine and a pitcher of beer the previous night, NHK said.
Japan Airlines said the flight was delayed more than an hour and had to be operated by the remaining two pilots.
The plane departed London after a delay of one hour and 9 minutes.
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Jitsukawa had nearly 189 mg of alcohol per 100 ml of blood in his system, which is nearly 10 times the permissible 20 mg for a pilot.
In a statement JAL said: "The Company does not condone the individual's actions, as safety remains our utmost priority".
Under Japan's Road Traffic Law, drivers are considered to be driving under the influence if they have an alcohol-per-liter-of-breath reading of 0.15 milligrams or higher.
"Although we conduct regular or unannounced safety inspections for airlines, detailed drinking regulations are left to the discretion of each company", said an official at the transport ministry's aviation safety and security department.
Jitsukawa was arrested at Heathrow Airport in London after failing an alcohol breath test.
The incident comes only a day after All Nippon Airways revealed a hung-over pilot had caused multiple flight delays.
The co-pilot will be sentenced on November 29, according to a United Kingdom court official.