National Air Traffic Services (Nats), which runs the Swanwick centre in Hampshire, was able to devise a work round to restore full capacity to the system at 11am, but a Nats representative said the source of the problem was not known. "An investigation is still continuing," he said.
Nats ran into problems when it tried to return systems from their night-time configuration, where a single controller manages a series of linked air space sectors, to the daytime configuration where a single controller manages each sector.
The air traffic body then cut the number of flights it was handling by half. At no time, Nats insisted, was passenger safety compromised by the failure.
Nats' systems have suffered three failures in the past two months that have led to flight delays and cancellations, but a spokesman told CW360.com, "Today's problems were the first failure particular to Swanwick."
Previous failures were caused when faulty data was fed into the Flight Data Processing System at West Drayton in Middlesex, near Heathrow. This triggered "multiple aborts" that eventually led to an automated shutdown of IBM S/390 mainframes.