A system failure affecting air traffic control workstations was to blame for disruption to thousands of passengers coming in and out of Britain’s biggest airports, officials said, as services returned to normal on Saturday.
A small number of flights remain delayed or cancelled at London’s Heathrow Airport – the world’s busiest international airport, according to its website.
Air traffic officials said Friday’s system failure occurred during a switchover of air controllers’ workstations, which are put into operation or placed on standby as demand varies.
“In this instance a transition between the two states caused a failure in the system which has not been seen before,” National Air Traffic Service said in a statement.
"The failure meant that the controllers were unable to access all of the data regarding individual flight plans which significantly increases their workload," Nats said, adding that traffic was then reduced.
British transport secretary Patrick McLoughlin had on Friday demanded a full explanation for the glitch that forced authorities to limit access to British airspace at one of the busiest times of year.
A parliamentary committee will begin an investigation into the disruption on Monday.
The disruption was the second such incident in just over a year to hit Nats's hub at Swanwick, Hampshire, in south England, one of two main centres.
However 38 flights were cancelled at Heathrow Airport, London on Saturday morning including one British Airways 6.55am departure to Dublin. Most flights to and from Irish airports are operating as normal.
While the UK’s air traffic control company Nats declared its systems are back to full operational capacity, the flight problems at some of the UK’s busiest thoroughfares could still be a reality for some passengers.
Dozens of flights were cancelled and many others delayed after a computer failure at Nats’ company headquarters at Swanwick, Hampshire, yesterday afternoon.
A spokesman for Heathrow said 38 flights are cancelled before 9.30am today “as a knock on ” from Friday’s problems.
Nats said at about 8pm : “Following a technical fault with the flight data system used by air traffic controllers at Swanwick, Nats can confirm that the system has been restored to full operational capability and a thorough investigation is continuing to identify the root cause.
“Although operational restrictions applied during the failure have been lifted, it will take time for flight operations across the UK to fully recover so passengers should contact their airline for the status of their flight. We apologise for the impact that this issue has had, and the delays and inconvenience caused.”
The company has ruled out a power outage as the source of the glitch at Nats’ state-of-the-art £700 million centre.
Aberdeen and Edinburgh were affected by the computer problem. Other airports that reported delays on Friday afternoon included Manchester, Stansted and Luton.
Budget flier easyJet said last night: "EasyJet has had to cancel 10 flights to and from London Gatwick, however all aircraft which were earlier diverted have all now continued to their original destinations. In addition, it is likely that other flights to and from the south of the UK will suffer delays this evening."
The airline said it had cancelled two Gatwick-bound flights scheduled for today.
Gatwick Airport said on Friday evening: “Some cancellations should be expected and passengers are advised to contact their airline for the latest flight information.
“All departing flights were affected for a period but the situation is improving and we (are) hoping to restore a near normal service later this evening.”
At Heathrow, a spokesman said on Friday there had been 70 cancellations out of about 1,300 scheduled flights. “They’re coming back to normal now,” he said.
The airport put extra staff on duty and were due to be open later than usual to try to get stranded passengers in the air.
In a statement on its website yesterday evening British Airways said: “While the system is slowly recovering, we anticipate the knock-on effects to take some time to resolve. Additional staff have been brought in to assist our customers and we have booked a large number of hotel rooms to accommodate those who have been disrupted.”
Birmingham Airport had experienced delays but reported its air traffic was back to normal by 8pm.
Britain’s transport secretary Patrick McLoughlin described the disruption as unacceptable.
“Any disruption to our aviation system is a matter of the utmost concern, especially at this time of year in the run up to the holiday season,” he said.
“Disruption on this scale is simply unacceptable and I have asked Nats for a full explanation of this evening’s incident. I also want to know what steps will be taken to prevent this happening again.”
PA