An air traffic control problem has hit hundreds of flights using northern European airspace.
Germany, Belgium, the Netherlands and Luxembourg were among the countries affected.
The problem was centred on the Eurocontrol radar system, based at Maastricht in the Netherlands.
Eurocontrol later confirmed the system had returned to normal capacity, but said the backlog of flights would mean delays continuing into the evening.
Eurocontrol said "equipment problems" affected its air navigation services for flights in airspace above 7,500m (24,600 ft).
About 700 flights have been affected, said Europe's air traffic control system.
The UK reported some delays to flights into and out of the country, but said no major problems had been experienced.
Flights over western Europe had to be cut by a quarter during the failure, which lasted from 1315 to 1330 GMT, a Swedish official told Associated Press news agency.