THOUSANDS of passengers at airports across Britain were left stranded this morning after a system fault at Hampshire's new Air Traffic Control Centre.

There were massive delays at the country's major airports - including Southampton, Heathrow and Gatwick - when half of the computers used to control flights went down.

The failure at the Swanwick base happened after a monthly routine upgrade of the computer system last night.

When staff arrived at the centre for the 6am shift this morning they discovered the work stations couldn't be used.

A team of six engineers was drafted in to try and fix the problem.

By 10.30am, 80 per cent of the computers were back on line.

At Southampton Airport, hundreds of holidaymakers hoping to fly to Majorca and the Channel Islands were left waiting for more than two hours

The story was repeated at airports across the country with delays in Glasgow, Edinburgh, Aberdeen, Teeside, Birmingham, Manchester and Cardiff - with some travellers facing delays of between half hour and two hours and other flights cancelled.

Short-haul passengers were the worst affected.

The system glitch - the third major one since the air traffic control centre opened in January - had a knock-on effect in Europe as short-haul incoming flights had to be grounded.

Now the National Air Traffic Services is carrying out a full investigation into what went wrong.

A spokesman said: "The system fault meant that we reduced the number of flights we handled by 50 per cent. We wanted to concentrate on the ones already up in the air. At no time were air passengers in any danger."

The spokesman added that resulting delays and possible cancellations were likely to affect every airport in Britain.

All other air traffic centres were operating as normal today.

Richard Everitt, chief executive of National Air Traffic Services, said services were experiencing serious delays because of a computer breakdown at the main air traffic control centre, at Swanwick, Hampshire.

He was unable to say when flights would be back to normal, but reassured travellers that the problem did not affect safety.

"There are no safety issues, I can assure you on that."

Britain's air traffic control system handles some two million flights every year through four centres - Swanwick, West Drayton, Manchester and one in Scotland.

At Southampton International Airport insurance salesman Chris Atkinson, 23, was waiting to board a flight to Newcastle, which was cancelled. He said: "I'm going home to see my friend who is in intensive care."

Graeme Somner, 80, retired from Christchurch, should have been catching the 10.20am flight to Jersey with his wife Hazel, 75. They will now be waiting until the next flight at 4.55pm.

Mr Somner said: "We've lost today."