It was found that his body contains 189 mg of alcohol per 100 ml of blood, although the allowable limit for pilots of 20 milligrams.
Speaking to the Asahi Shimbun newspaper, Japan's transport minister said the government would look into toughening regulations on alcohol consumption by pilots in the wake of the incidents.
The airline said the co-pilot was arrested Sunday at Heathrow Airport for violating British aviation law.
A JAPAN AIRLINES pilot who was arrested shortly before take-off at Heathrow Airport in London was nearly ten times over the legal alcohol limit, it has emerged. British police made the co-pilot take a blood test to confirm the results. The limit for drivers in Britain is 80 milligrams.
According to JAL, Jitsukawa may have improperly cleared its standard alcohol check, as the airline's breath-testing equipment did not detect any issues. He is now in custody and will be sentenced on November 29 at the Isleworth Crown Court.
After the bus driver alerted authorities, the co-pilot, Katsutoshi Jitsukawa, 42, was arrested at Heathrow - 50 minutes before his flight to Tokyo.
Kim Jong-un amenazó con reanudar programa nuclear
La prensa oficial dio pocos detalles, pero indicó que las pláticas se dieron en " un ambiente amistoso y de camaradería ".
"Safety remains our utmost priority", the airline said in a statement.
The last-minute sickie forced the airline to delay five flights linking Okinawa island and smaller regional islands, affecting 619 passengers.
But under Japan's current system, while plane crew members are banned from drinking within eight hours of working, there is no legal limit set and breath tests are not required.
JAL said the flight was delayed more than one hour and had to be operated by the remaining two pilots.
The airline will now also involve airport staff in alcohol checks rather than allowing pilots to test each other, Kyodo news agency reported.