The men blamed a lack of sleep during the previous day and a half, The Daily Telegraph reported Thursday.
The admissions were made to the Civil Aviation Authority, which did not identify the airline involved but said the company was based in the United Kingdom.
The pilots told the watchdog agency longer shifts over the holiday season caused them to get no more than five hours sleep in the previous 36 hours.
Proposed rule changes would cause pilots to work seven flights in a row, the British Airline Pilots Association has warned, and could lead to pilots being awake for 22 straight hours.
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