Passengers are facing widespread flight disruption after a computer failure at the UK’s air traffic control centre.
Nats said it was in the process of returning to normal operations after a “technical problem” at its Swanwick control centre caused delays and grounded some flights.
Problems were reported around the UK.
They included delays at Heathrow and Gatwick where departing flights were grounded for a time. Other UK airports reported knock-on effects.
Reported problems around the country include:
Heathrow: Flights are “currently experiencing delays” but planes now landing and taking off
Gatwick: Flights are now departing but still subject to delays
Stansted: Flights still landing, no flights departing
Bristol: Limited departures reported
Luton: All flights experiencing delays but planes now leaving
Edinburgh: No queues but passengers being advised to check with their airlines
Southampton: Experiencing ”problems”
Oxford: Experiencing “some delays”, mainly to services arriving from overseas
Leeds Bradford: All flights out and most flights in suspended until 1900
Aberdeen: Reported an “impact” on operations
Passenger Simon Peach: “We are still on the plane but it sounds like things are moving in the right direction”
One source told the BBC the problem was caused by a computer glitch that co-ordinates the flights coming into London and puts the flights in sequence as they come into land or take off.
He described it as a “flight planning tool problem”.
Travel body Abta encouraged passengers expecting to take a flight to contact their airline.
BBC journalist Joe Inwood was at Luton Airport when the flights stopped
Manchester Airport said it was unaffected by the incident and was ready to accept diverted flights.
Vicky Lane, a passenger on a grounded London to Dublin plane at Gatwick said: “We’ve been stuck on a Ryanair flight… for over an hour.
“The doors are open and we’re really cold. I’m not sure when we will be leaving.”
Another passenger, on a flight to Paris, said his plane had “circled around the Lake District for half an hour before turning back to Edinburgh”.
Ed Bott told the BBC he was: “Currently sitting on the tarmac. None the wiser. Waiting for news as to what’s happening.”
Swanwick controls the 200,000 square miles of airspace above England and Wales, cost £623m to build, and employs about 1,300 controllers.
But the facility, which handles 5,000 flights every 24 hours, has had a troubled history.
It opened in 2002, six years after its planned commissioning date – a delay which National Air Traffic Services (Nats) said was due to problems with the software used to power its systems.
Almost a year after it opened, a senior air traffic controller raised concerns with the BBC about health and safety standards and complications with radio communications – which he said cut out erratically.
Technical problems and computer faults hit flights in 2008 and again last summer. And, in December 2013, problems with the internal telephone system then caused further delays.
Aviation journalist David Learmount said the IT problem would cause “major disruption” but would be resolved by Saturday.
“This impacts not just people within the UK, it impacts flights heading here from anywhere – anything heading this way will be told some of them can’t be accepted, and they will have to go back to where they flew from or consider diverting to other countries,” he told the BBC.
The RAF – which has its own air traffic control systems – said the UK military was unaffected.