London air traffic control investigates weekend chaos

The UK National Air Traffic Service (NATS) is still investigating the cause of a computer failure that left thousands of passengers stranded over the weekend.

The flight data processing system went down at 09:30 BST on Saturday, and technicians spent the next three and a quarter hours bringing the system back up.

The system produces strips of paper that contain information about the planes, such as where a flight originated and where it is headed. In the absence of the computer, air traffic controllers produce the strips of information manually with paper and pen.

According to a spokeswoman for NATS, the pen-and-ink method is just as accurate, but much slower. She stressed that NATS lost only an element of the air traffic control system, and that all radar and radio communication systems were unaffected.

"OK, we did resort to pen and paper," she said. "But it's a fool-proof system for producing the information."