Due to the arrest, the flight's departure for Haneda airport scheduled for 7pm on Sunday local time was delayed by 1 hour and 9 minutes.
He was caught after the driver of a crew bus smelled alcohol and called the police, according to Japanese broadcaster NHK.
The Japan Airlines pilot - who had been due to fly a Boeing 777 plane, which holds up to 244 passengers - was reported and arrested at the airport.
A Metropolitan Police spokesman said that Jitsukawa pleaded guilty yesterday to exceeding the alcohol limit at Uxbridge magistrates' court.
Tests found the 42-year-old first officer had 189 milligrams of alcohol per 100 milliliters of blood in his system, nearly 10 times the 20 milligrams limit for a pilot.
Jitsukawa, 42, attributed the elevated alcohol levels to a bout of serious drinking the previous night in his hotel bar and room, according to NHK.
The flight departed after a 69-minute delay.
The normal legal limit for driving in the United Kingdom would be 80 milligrams per liter.More news: Israel fires on Palestinians launching arson balloons
Jitsukawa was charged with performing an aviation function with alcohol in his blood over the legal limit. That is probably why he landed up at the Heathrow airport highly drunk and ready to board the flight.
Japan Airlines officials said they believed the pilot had tampered with the test to hide his drinking.
JAL subsequently apologized for the breach and admitted that an in-house breath test was not conducted properly.
JAL had prohibited its pilots from drinking alcohol 12 hours before getting on their flights.
The transport ministry on Thursday issued a document directing all Japanese airlines to report by end of the month measures being taken to control drinking by flight crew. He was remanded in custody and will be sentenced on 29 November at Isleworth Crown Court.
Japan Airlines has apologised for the incident, saying that "safety remains our utmost priority" and it will "implement immediate actions to prevent any future occurrence".
His heavy drinking also forced the company to operate the flight from Heathrow airport to Haneda airport in Tokyo with two pilots rather than the normal three.