Airports around the UK have been returning to normal, although almost 40 flights were cancelled at Heathrow, the day after a computer failure at the national air traffic control centre.
National Air Traffic Services (Nats) said a technical fault in the flight data system at its Swanwick centre, in Hampshire, had caused the problem.
This resulted in widespread disruption at airports around the UK on Friday.
Transport Secretary Patrick McLoughlin said the situation was “unacceptable”.
The Swanwick centre was restored to “full operational capacity” on Friday afternoon, Nats said.
Heathrow Airport said 38 flights due to arrive or take off before 09:30 GMT on Saturday had been cancelled but the subsequent schedule was “back to normal”.
A Heathrow spokesman said the cancelled flights could not be rescheduled because the airport ran at 98% capacity. He said passengers would be rebooked on other services.