The transport ministry issued a business improvement order to Japan Airlines Co. on Friday over a pilot who was convicted in the U.K. for heavy drinking that delayed the start of a London-Tokyo flight.

The order, the third most serious reprimand after business license revocation and business suspension orders, was issued after a JAL co-pilot was given a 10-month sentence in the U.K. for having a blood-alcohol level about 10 times higher than the legal limit before boarding the flight in October. He has since been dismissed.

"We're really sorry for customers who trust and board our flights. We will take drastic measures to address the issue," said JAL President Yuji Akasaka after receiving the order.