Thousands of travellers have been stranded in UK airports after a major air traffic control computer system crashed.

Hundreds of flights were cancelled or delayed after the computers which provide flight schedule information for air traffic controllers broke down in the middle of Wednesday afternoon.

All UK flights were stopped for 20 minutes, while those in London and the South-East were affected for much longer.

By Wednesday evening, although the computers were back up and running, flights leaving the region and those inbound from Europe were still operating at half the normal rate.

Richard Wright, a spokesman for National Air Traffic Services (Nats) said the region would not be fully back up until Thursday morning.

'No safety issues'

He explained that the glitch meant all the routes and schedules information normally produced by the computer - called flight strip - had to be prepared by hand.

Mr Wright said the issue was one of speed only, and there were no safety implications.

"There was no loss of radio communication between the pilots and the controllers and no loss of information on the radar screens."

Mr Wright said the failure happened to a system based at West Drayton, near Heathrow in west London.

He said it was not connected with the computers at the new Swanwick air traffic control centre in Hampshire, which was dogged with computer problems before it opened six years late in January.

A very similar incident occurred two years ago, delaying soccer legend Sir Bobby Charlton on his way to see England's crucial Euro 2000 match in Belgium.

Nats was privatised last summer, but ran into financial difficulties after the 11 September attacks on the US, which caused a slump in trans-Atlantic traffic from which it makes about 44% of its income.

Transport Secretary Stephen Byers confirmed last week that the service would be bailed out with �30m of public money and a �30m bank loan.