National Air Traffic Services, the company that controls U.K. airspace, said the Flight Data Processing System at the West Drayton control center crashed after overnight testing. As a result, information about flights entering controlled airspace had to be hand-entered into the rest of the control system, resulting in a drastic reduction of capacity and a temporary ban on flight departures.
Although the overnight testing was thought to have concluded successfully, the system subsequently failed at about 10 p.m. PST Wednesday (6 a.m. BST Thursday), when it was restarted and entered an unstable mode. It was operational again at 10:45 p.m. and declared stable at 11:02 p.m.
A similar problem with the processing system brought chaos to U.K. airports in 2002, with passengers suffering two-hour delays as a result of the glitch. That time, the problem was caused by an overnight software upgrade. There was no software upgrade this time, an NATS spokesman said, and no operating code had been changed. This is the first time that this class of failure has happened, he said, adding that an investigation into its causes is now under way.
The U.K. government owns slightly more than half of NATS, with a consortium of airlines and employees owning the rest. The organization hit severe difficulties, following the slump in air travel after Sept. 11, 2001. This problem was compounded by a catalogue of computer system errors.
Rupert Goodwins of ZDNet UK reported from London. Andrew Donoghue contributed to this report.