Jitsukawa admitted to the improper conduct at Uxbridge Magistrates' Court in west London on Thursday and will remain in custody until he is sentenced on November 29.
He was supposed to pilot the flight JL44 Japan Airlines (JAL) in Tokyo, but failed the test in 50 minutes before departure.
According to BBC, the 42-year-old first officer was found to have 189mg of alcohol per 100ml of blood in his system - whereas the legal limit for pilots is only 20mg.
Worryingly, the man cleared an in-house breath test but was arrested by British police after his bus driver became concerned with his behaviour while driving the pilot to Heathrow Airport, reports 7News. He is now in custody and will be sentenced on November 29 at the Isleworth Crown Court.More news: US adds 250,000 jobs, pay growth fastest since 2009
He confessed he drank two bottles of wine and a pitcher of beer the night before his flight.
JAL said the flight was delayed more than an hour and had to be operated by the remaining two pilots.
The incident came a day after another Japanese carrier apologised for multiple delays after a hungover pilot called in sick.
Japan Airlines issued a statement of apology, saying "safety remains our utmost priority" and that they will "implement immediate actions to prevent any future occurrences".More news: Irish PM: Brexit is undermining N. Ireland's peace accord
Japan's transport minister has said he will tighten rules about alcohol consumption by flight crews after a series of incidents in the industry.
In May, a Japan Airlines flight attendant was caught drinking a beer in a bathroom during a flight, Kyodo reported.
Katsutoshi Jitsukawa, 42, had nearly 10 times more than the legal permitted amount of alcohol in his bloodstream when he was arrested, the Metropolitan Police said.More news: Guardiola says managing in England is ‘dream come true’