One in six UK airline pilots has woken up in the cockpit to find their co-pilot asleep

More than half of British pilots have fallen asleep in the cockpit of a passenger plane.

And alarming research has revealed that one in six commercial pilots has woken up at the controls - only to see that their co-pilot is dozing too.

The findings were revealed yesterday, following reports that two pilots fell asleep on a British passenger plane last month.

The captain and co-pilot of the Virgin Atlantic Airbus A330 blamed their long shifts.

The Civil Aviation Authority described it as an isolated incident, and experts said passengers' lives were not at risk because the plane would have been on auto-pilot.

A CAA report said the crew were 'suffering from symptoms of severe fatigue'.

It added: 'Both members of flight crew had only five hours sleep in two nights due to longer duty period with insufficient opportunity to sleep. Both crew rested for 20minute rotations and fell asleep.' Sir Richard Branson's Virgin Atlantic admitted its plane was involved, but denied reports that both pilots were asleep at the same time.

A spokesman said the captain and co-pilot were sleeping in alternate 20minute intervals - an approved practice known as 'in-flight napping'.

This was contradicted by the CAA report, which clearly stated 'pilots asleep'. The incident was logged after one of the pilots reported it.

The CAA has recorded two previous incidents of pilots falling asleep in the cockpit.

However, the British Airline Pilots Association (Balpa) said the industry regulator only recorded episodes that were reported - and warned that pilots fell asleep with alarming regularity.

The union, which represents three-quarters of pilots in the UK, said demanding flight schedules and busy airline rotas were to blame.

Research by Balpa found that half of all pilots said tiredness was 'the biggest threat to flight safety'.

Some 56 per cent said they had fallen asleep in the cockpit. Of those, 29 per cent - about one in six of all pilots - said they woke up to find their co-pilot was also asleep.

The research was carried out ahead of a European Parliament vote on EU rules for flying hours, which takes place on Monday.

Balpa warns the new regulations will put lives at risk as they will legalise shift patterns that could see pilots kept awake for up to 24 hours.

In its poll of 500 pilots, 84 per cent said their flying abilities had been compromised during the past six months. Some 43 per cent experienced problems once a month.

Only half said their airline would back them if they refused to fly because of fatigue.

Balpa general secretary Jim McAuslan said: 'British pilots want to make every flight a safe flight and tiredness is the biggest challenge they face.'

Transport ministers were warned of the dangers of sleepy pilots nine months ago, but said it was not 'a reported flight safety issue'.

A CAA spokesman stressed that, if approved, new European rules 'will increase our oversight role of airline operators and place firm obligations on airlines to introduce comprehensive fatiguemanagement policies and monitoring systems'.

A spokesman for the Department for Transport added: 'The Civil Aviation Authority is satisfied that the proposed requirements will improve safety across the EU as a whole.

'Flight Time Limitation requirements are there to ensure that pilots and other crew members do not operate aircraft with unsafe levels of fatigue.'

They claimed the proposals 'go further than current requirements, by obliging airlines to plan rotas and manage crew duties to actively address the risk of fatigue'.