George La Perle, 49, who flew for Delta Airlines, was found to be four and a half times over the alcohol limit.
He told security staff he was flying to New York. But his actual destination was Detroit, the Daily Express reported. He has been jailed for six months.
American citizen La Perle, from Boston, who has 20 years flying experience, was one of three pilots in the Boeing 767 scheduled to fly Nov 1, 2010.
The plane had up to 241 passengers to the US.
Heidi Stonecliffe, prosecutor at the Isleworth Crown Court, said there could have been "extremely dangerous and potentially disastrous consequences".