European air travelers faced mass disruption on Tuesday with around half of all flights at risk of delays following a technical problem at Eurocontrol, the agency in charge of the continent's skies.
Several of the EU's biggest airports, including Amsterdam's Schiphol, warned of problems and advised passengers to check on their flights because of the computer breakdown.
"Today 29,500 flights were expected in the European network. Approximately half of those could have some delay as a result of the system outage," said a statement from Eurocontrol.
The Brussels-based agency, which coordinates European air traffic control operators, said the cause "has been identified and action is underway to return to normal operations" but that that would not happen until "late this evening".
The breakdown comes a day after the Easter holidays when many travelers are on the move around Europe, and as commuters across France faced disruption from a massive rail strike in protest at President Emmanuel Macron's reforms.
"We have never had anything like this before," a Eurocontrol spokesman told AFP.
Brussels airport said departures were limited to 10 flights an hour. The Belgian airport manages 650 flights a day, according to its website.
Several airports across the continent warned of problems, with Schiphol saying that the "system failure" at Eurocontrol could have "possible consequences" for departures.
Helsinki, Prague and Copenhagen airports also said traffic was facing delays.
Eurocontrol said that there had been a "failure of the Enhanced Tactical Flow Management System", which tracks and manages traffic demand across the continent.
"Contingency procedures are being put in place which will have the effect of reducing the capacity of the European network by approximately 10 percent," the agency said in an initial statement.
It added that flight plans filed before 1026 GMT were "lost" and asked airlines to refile them.
It added that air traffic control had not been directly affected and "there are no safety implications arising from this incident".
UAE files ICAO complaint over Qatari flight interceptionsThe UAE on Monday lodged a complaint with the International Civil Aviation Organization after it said Qatari jets approached civilian flights last ... Gulf
Kuwait Airways flights to Germany in jeopardy after it rejects Israeli passengerA German official warned the Kuwait national carrier it might lose flights to Germany, after it rejected an Israeli passenger two years ago. German ... Aviation & Transport
UAE says civilian flight paths will not change after Qatar fighter jet incidentThe United Arab Emirates will not change its civilian flight paths, the chairman of its General Civil Aviation Authority said on Tuesday, a day after ... Gulf
UAE expat community show support to family after husband dies on Emirates flightThe UAE’s expat community has come together in a time of need after a young British family residing in the country lost a husband and father ... Gulf