Updated

Flights are being delayed at Britain's busiest airports because of a technical problem at the country's main air traffic control center.

National Air Traffic Service said it was having a problem switching between nighttime and daytime operations at its control center in Swanwick, southern England. It said: "This may result in some delays, for which we apologize."

It said technicians were trying to fix the problem.

Heathrow Airport — Europe's busiest — is showing delays of an hour or more on many morning flights Saturday.

London's Stansted airport said departing flights were seeing delays of between 30 minutes and 2 hours because of restrictions on air space and the flow of planes. Gatwick airport said 20 percent of flights were being delayed.