TENS of thousands of airline passengers were today facing delays after the UK's air traffic control system crashed.Airports across Britain were hit, with flights being grounded immediately and passengers facing hours of delays to clear the backlog.

TENS of thousands of airline passengers were today facing delays after the UK's air traffic control system crashed.

Airports across Britain were hit, with flights being grounded immediately and passengers facing hours of delays to clear the backlog.

Heathrow, Gatwick, Manchester and Stansted were all affected by the computer glitch.

Passengers were being warned to check with airlines before leaving home to travel.

The national system went down at around 6am this morning and controllers had to switch to manual operations.

The privatised National Air Traffic Services, (Nats), the firm that operates air traffic control in the UK, said passenger safety was never put at risk despite the computer crash.

Mark Pearson, spokesman for Heathrow Airport, which handles 1,250 flights a day, said: "There is serious disruption at Heathrow as a result of the air traffic control situation. There is an average of two-hour delays on departures and restrictions on arrivals.

"We are advising passengers to check with their airlines before leaving home."

Gatwick was operating around 10 outbound flights per hour, but would normally handle 30 to 40. Stansted in Essex was operating at around 60 per cent capacity early this morning.

Mark Davison, a spokesman for Stansted Airport, said early this morning: "All the arrival flights got in no problem, but the departure flights have been subject to delay.

"By 8am we were at 60 per cent capacity and we are hoping to be at full capacity by 9am.

"The average delay with a flight is probably around two to three hours."

He added the problem was likely to have knock-on effects on the bigger airlines.

British Airways said the size of the problem was likely to cause "severe delays throughout the day".

Adrian Yalland, spokesman for Nats, said their computer system had crashed just after6am but the system was up and running again by 7am and was now "fully operational".

He said they believed they had located the problem to an operations centre in West Drayton, near Heathrow Airport.

He added: "The fault is thought to lie with the data processing system. We think it is to do with the flow of data.

"The reasons why planes were grounded was because we couldn't let them into the air which would add more complications. We wanted to ensure the safety of flights in the air.

"The system is not going to go down again."

It is not the first time the Nats system has gone down leaving passengers in the lurch at airports.

A similar problem hit thousands of air passengers in the summer of 2000.

Have you been affected by the computer crash? Contact the Evening Star newsdesk on 01473 324788. Or write in to Your Letters, Evening Star, 30 Lower Brook Street, Ipswich, IP4 1AN or e-mail eveningstarletters@eveningstar.co.uk or visit the forum at www.eveningstar.co.uk