Tens of thousands of air passengers across northern Europe faced delays on Friday after an air traffic control problem affected about 700 flights.
A computer outage at a radar facility of the continent's Eurocontrol system in the Netherlands lasted about an hour and a half.
Eurocontrol, based in Brussels, Belgium, estimated that 700 flights would be affected by the problem in the Maastricht facility and delays were expected to add up to 15,000 to 20,000 minutes.
The problem halted flights above 24,606 feet, according to Axel Raab, a spokesman for German air traffic control. Pilots could choose to fly at lower altitude, although that airspace could clog quickly, Raab said. The Maastricht facility handles around 5,500 flights a day.
Fred Koennemann, a spokesman for Eurocontrol in Maastricht, said the system experienced a computer problem at about 12.50pm on Friday but started recovering gradually about half an hour later and was back to full capacity by 2.30pm.
Air traffic controllers there usually handle about 200 flights an hour but the capacity was temporarily down to 60 flights an hour, Koennemann said. He added that the situation would be back to normal on Saturday
Radar failures cause delays because they force air traffic controllers to increase the separation between planes up to five minutes, or about 40 nautical miles, thus reducing flow through the affected air space.
Nearly 30,000 flights were using European airspace on Friday. Officials in Britain, Poland, Austria, Italy and the Baltic countries said their airspace was not affected.
