(Bloomberg) — London's airports sought to restore orderly service after a computer failure caused delays at Heathrow, Europe's busiest hub, raising concern about the reliability of a major control center that's suffered repeat malfunctions.

The fault, which occurred mid afternoon local time in the U.K., was due to a technical issue at the Swanwick air-traffic center and did not involve a power outage, according to the NATS authority, which said it is "restricting traffic volumes in accordance with capability we currently have in our system."

Today's fault, which also affected other airports in southern Britain and rippled as far north as Manchester, follows a sequence of similar incidents. In July last year, NATS had to restrict the number of aircraft flying across the south of England and those taking off from airports. Swanwick, on which Lockheed Martin Corp. was prime contractor, opened almost six years late in 2002 and at least 30% over budget after repeated software glitches.