Flight chaos after computer glitch

Thousands of passengers were stranded at UK airports today after a routine computer test caused chaos.

Hundreds of passengers jets were grounded this morning when the air traffic system crashed.

The problem was fixed within an hour but the backlog means travellers are facing delays of up to three hours through today and into tomorrow - the busiest day of the week.

There was misery at Heathrow, Gatwick, Stansted and airports around the country as queues built up at departure desks. Anger grew as it emerged that the system failure was caused by the National Air Traffic Services (NATS) testing new software at West Drayton overnight. Air traffic controllers had to give priority to guiding down jets already airborne and flights waiting to take off were suspended or severely restricted.

Families on half-term holidays were caught up in the ensuing chaos. Also trapped were the England A rugby team and former chancellor Kenneth Clarke. Travellers planning to fly today are strongly advised to contact their airlines before setting off. Fewer than a third of timetabled flights took from Heathrow between 6am and 8am - 41 flights from a scheduled 150. Most flights from terminals one to four were running at least an hour behind schedule.

A spokesman for British Airways at Heathrow said: "It's chaos. Fortunately, it happened early in the morning, but the backlog of passengers is building up. It is every airline's nightmare." Between 6am and 7am - the busiest time of day - Heathrow was at a standstill. All 45 flights scheduled to take off were grounded. Passengers waiting at the airport were tired and angry.

Sam Marshall, 29, from Wokingham, had to be in Manchester for a business meeting. Miss Marshall, who works for a pharmaceutical company, said: "I will have to cancel the meeting. I am now queuing for a refund but even this queue is about a mile long."

Kai Strobach, 36, from Hounslow, was planning to fly to Germany with her fivemonthold daughter Elsa.

Miss Strobach said: "I am prepared to wait here for another two hours and if my flight is not leaving by then I'm going to go home. I have a baby with me and I can't hang around here all day."

By noon BA, Britain's biggest carrier, had cancelled 27 flights - 14 short-haul and one long-haul from Heathrow to Washington; five short-haul from Gatwick and seven services from regional airports.

BA operates 800 flights a day from Heathrow and Gatwick and 1,200 across the UK. At Gatwick only around 10 outbound flights operated early morning instead of the usual 30 to 40.

An airport spokesman said: "We have flights leaving every six minutes, which is only a third of our capacity. Passengers can expect severe delays."

At Stansted, just 60 per cent of flights were operating and passengers were warned to expect delays of three hours. Flights were cancelled and some passengers were booked on to later services.

Regional airports including Manchester were also hit. A passenger at Glasgow airport described the situation as "a complete shambles". A spokeswoman for British Airways there said: "We are expecting some delays. We do have some flights getting off but there are delays of an hour or two."

Transport Secretary Alistair Darling blamed the breakdown on years of underinvestment, adding: "Systems do break but we are now putting the money in and it is making a difference and delays caused by air traffic failure have decreased dramatically in recent years."

Richard Everitt, NATS chief executive, said: "I would like to apologise to all passengers and tell them that we are doing our best to minimise our disruption to them." He added: "The system has to be upgraded."

But computer experts questioned why it was necessary to carry out tests on an operational rather than a simulated system. West Drayton in west London covers all airports in London and the South-East.