Half a million airline passengers across Europe face delays and cancellations for the rest of the day as a result of a systems failure at the Eurocontrol centre in Brussels.
Eurocontrol, which coordinates air traffic for 41 member states, tweeted: “There has been a failure of the Enhanced Tactical Flow Management System [ETFMS].
“Contingency procedures are being put in place which will have the effect of reducing the capacity of the European network by approximately 10 per cent.
The average daily traffic in April in Eurocontrol’s 41 member states is almost 30,000 flights, which potentially means that 3,000 flights — and up to half a million passengers — could face disruption.
The system is designed to match demand from airlines with capacity in the crowded skies above Europe. When airlines file flight plans, ETFMS calculates a pathway according to data on available airspace and allocates slots accordingly. The relevant national air-traffic providers are notified, reducing the complexity of communication.
Eurocontrol says: “It is a key enabler of the air traffic flow and capacity management services.”
Pilots and air-traffic controllers across Europe were told: “All attempts to reactivate ETFMS proved unsuccessful.”
Later, Eurocontrol tweeted: "The issue with the ETFMS has been identified and work is progressing to recover the system, which is expected to occur late this evening."
Contingency Level Red has been declared, meaning that the central role played by Eurocontrol has been abandoned.
All flight plans filed before 11.26am, British time, have been lost by the system, and airlines have been asked to re-file them.
Departure slots will be rationed, which is likely to mean delays on the ground building rapidly. If gates are blocked, arriving aircraft will have to wait for planes to leave.
Crowded airports such as Heathrow, Gatwick, Amsterdam and Frankfurt are particularly vulnerable to disruption. Paris Charles de Gaulle is unlikely to be so badly affected, because one in four Air France flights have been grounded by a strike.