Air traffic in and through Britain was badly disrupted this morning by a computer breakdown at National Air Traffic Services.
The air traffic control system was fully restored after about two hours.
At least 21 flights were delayed from Dublin, Cork and Shannon. Some Air France flights that cross London airspace were also affected.
Intending passengers were being advised to check in as normal and to contact their airline.
At Gatwick, departures were severely delayed and at Manchester all flights were grounded for just under an hour.
Britain's national air traffic control computer system at Swanwick, which controls all flights in and out of London, crashed at 6am this morning. The underlying fault may have been at the operations centre at West Drayton.
Flights that did leave or arrive during the breakdown were being operated manually by air traffic controllers.
