Flights over Britain have been hit by delays and cancellations after technical problems struck the country's air traffic control system for the third time in two months.
The National Air Traffic Control Service said the glitch at its new control centre in Swanwick, southern England, started shortly before 7 a.m. - a peak time for transatlantic arrivals and European departures.
A spokesman said flights had been halved because of a technical problem that was affecting some computer terminals, but he said passenger safety was not affected.
Britain's biggest airport, London Heathrow, said it was advising passengers to contact their airlines to find out whether their flights were delayed or cancelled.
The second biggest airport, Gatwick, said flights in and out were delayed by up to two hours.