One in five airline pilots suffers from fatigue in the cockpit at least once a week and their abilities are compromised as a result, a study suggests.

Of the 492 pilots who responded to a questionnaire commissioned by the pilots' union Balpa, 45 per cent said they were experiencing significant tiredness and more than 75 per cent said they had failed to report incidents of fatigue to their airline during the past six months.

The study was conducted by University College London ahead of a ruling by the European Aviation Safety Agency that Balpa believes could weaken regulations guarding against pilot tiredness.