James Glen, 38, admitted communicating information about a bomb hoax on an Etihad Airways flight heading from Abu Dhabi to Heathrow on January 24.
He told a flight attendant that a passenger had a gun and had threatened to blow himself up, Chelmsford Crown Court heard.
The plane, carrying 163 passengers and 15 crew, was redirected to Stansted Airport, Essex under Royal Air Force (RAF) escort.
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