Thousands of travellers were delayed yesterday after a key air traffic control system failed.
National Air Traffic Services (Nats) said that the Flight Data Processing System (FDPS) at its West Drayton centre went down between 4.11pm and 4.30pm on Wednesday afternoon (27 March).
The system prints the paper strips that controllers use to plot the movements of planes. When the system failed the strips had to be written out manually.
"That takes time so planes get delayed," said a Nats spokesman. "The engineers have identified the technical nature of the problem and know how to stop it happening again."
Although the hardware for the FDPS was upgraded from an IBM 4381 to an IBM 0/S390 in Autumn last year, the application still contains some code created in the 1970s. Nats said there are software upgrades to the system around once a month.
The same system crashed four times in 2000 causing massive delays, and is not scheduled for replacement until 2007.
"Ultimately the system will move to electronic strips but it's easier to use the paper strips at the moment. In the future replacing the paper strips will make things more efficient," the spokesman told vnunet.com.
Airspace over London and the south east up to 20,000 feet is still controlled from the site at West Drayton.
The control of high level airspace is now done from the air traffic control centre at Swanwick, which opened in January five years late and £180m over budget.
Late last month flights were delayed by an upgrade to systems at the new site.
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