London airspace is closed until 7pm today due to a technical failure at the National Air Traffic Services (NATS).
European air traffic control coordinating organisation Eurocontrol said: There has been a failure of the flight data computer server at London ACC [area control centre].
Engineers are working on the problem and more information will be given will available. Only already airborne traffic will be accepted.
The UK's air traffic coordination organisation NATS said at 16.15 UK time that systems had been restored. However, based on the experience of previous outages, this process could last some hours.
The failure came a week after NATS announced a £2.4 billion Europe wide project to upgrade the continents air traffic management systems, with four airline groups, operators of 25 airports and 11 air traffic control provider joining forces.
The control centre suffered a server failure almost exactly one year ago.