NHK has learned that a Japan Airlines pilot was replaced with a substitute after alcohol was detected on his breath in a preflight test last month.
The 50-year-old pilot was due to work on a flight from Shanghai to Narita, near Tokyo, on April 29.
He was discovered to have an alcohol level of 0.11 milligrams per liter of breath.
JAL says he admitted drinking about 1.4 liters of wine and beer with a copilot in a hotel room the evening before the flight.
New government rules ban crewmembers from flying if any alcohol is detected.
JAL said it takes a serious view of the incident that occurred despite its ongoing efforts to prevent alcohol-related problems involving flight crew.
A Japan Airlines copilot was sentenced to 10 months in prison in London last year after failing a breath test.