Passengers wait for the airtraffic system to return to normal at London Heathrow airport, June 3.   

The electric screens display all flights canceled and suspended at Heathrow airport, June 3.

Airplanes are ready to take off at London Heathrow airport, June 3.

     LONDON, June 3 (Xinhuanetnet) -- Thousands of air passengers are facing travel chaos at airports across Britain on Thursday after atwo-hour computer breakdown of an air traffic control system grounded f lights across the country.

    "There is serious disruption at Heathrow. There is an average of two hour delays on departures and restrictions on arrivals," said a spokesman for Heathrow, one of the world's busiest international airports which handles 1,250 flights a day.

    At Gatwick airport, another major airport near London, flights were landing normally but departures were operating in a very restricted flow rate, a spokesman said.

    British Airways said all its flights were subject to disruptionand cancellations throughout the day.

    A spokesman for National Air Traffic Services (NATS) said: "We are now dealing with the backlog of delays. It affected all airports in England and Wales."

    "Our computer system is now fully operational and safety being our primary concern we are now working to make sure those aircraftin the air and in need of landing should be able to do so to clearthe delays," he added.

    The NATS spokesman said its computer system went down at about 6 a.m. at West Drayton, north of Heathrow, which controls air traffic over southeast England and all planes to and from London'sairports. The system was running again two hours later but the backlog of flights threw airports into chaos throughout the country.

    Chief Executive Richard Everitt of the NATS told the BBC that the failure followed overnight testing of an upgrade to its FlightData Processing system in West Drayton.

    "We will now investigate why there was this problem - clearly it was not an anticipated problem - a lot of work will be done today to understand why we had problems with this testing," he said.

    The breakdown has cast doubt on the reliability of Britain's semi-privatized air traffic control system which, under NATS, has been undergoing a long-term modernization program.

    Transport Secretary Alistair Darling insisted Britain's air traffic control system is "very good" compared with other countries, stressing that "if you look at the delays caused by airtraffic control failure they have come down dramatically over the last few years."

    "If you want to know what is wrong with transport in this country it is that over decades successive governments did not spend enough on the infrastructure and air traffic control is no different," he said. "We are putting the money in and it is makinga difference." Enditem

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