The serious delay in re-starting the computer would prompt a major investigation within the National Air Traffic Service.

BBC: Computer crash delays 6,000 passengers

For example, the National Air Traffic Service, which has presided over one of the worst computer-procurement failures at its much-delayed Swanwick control centre, is outside parliamentary audit.

ECONOMIST: Government

The National Air Traffic Service has previously said there were 200 flights through British airspace in the past five years by the CIA planes associated by campaigners with rendition.

BBC: NEWS | UK | UK Politics | 'Rendition flights' landed in UK

The UK's National Air Traffic Service (Nats) said trans-Atlantic flights would be able to operate to and from the re-opened airspace, but stressed this did not mean all such flights would resume.

BBC: Volcanic ash: Flight chaos to continue into weekend