Confidence in strength of system: NATS chief

The chief of UK air traffic control has pledged that the computer glitch which brought air traffic to its knees on Friday will cause no further disruption over the holiday season.

NATS chief executive, Richard Deakin said: “Failures like this are extremely rare, but when they occur it is because they are unique and have not been seen before. If they do occur, root causes are identified and corrections made to prevent them happening again. We have never seen a repeat occurrence once a fix has been made. Following the issue on Friday, the root cause was identified, a correction put in place and we do not expect that failure to repeat.”

“Once the backlog in the network has been caught up over this weekend, this issue will not cause further disruption over the holiday season. We are confident in the strength of the systems and the people we use to successfully manage over two million flights every year.”

Passengers flying to and from London were faced with severe flight disruptions after the system failure at NATS area control centre at Swanwick. Although the airspace was not closed, flights were halted at some of the country’s major airports.

Airports in other parts of the country such as Birmingham and Manchester, in central and northern England, were unaffected by the technical problem although Heathrow, Gatwick, Stansted and Luton were severely affected.

NATS said that the problem had been caused by the software running Swanwick controller workstations preventing them from switching from standby to operational mode, blocking data on individual flight plans. This significantly increased workload and meant controllers had to reduce the traffic into and out of the UK network.

Speaking on the BBC News Channel on Saturday Deakin said that a ‘delinquent’ line of code has been discovered in 4 million lines of code had been responsible.

“The challenge is that we have around 50 different systems at Swanwick and around four million lines of code. This particular glitch was buried in one of those four million lines of code,” he said adding that the business was spending an extra £575 million over the next five years to update its systems.

One expert tells Air Traffic Management: “NATS seems to imply that the problem was in the en-route system NERC, not the NAS flight data processing system, but in the interface between the two, associated with bandboxing (combining) sectors in London area centre. The two systems probably somehow got out of sync. This explains why Prestwick was not affected.”

Last December, a computer glitch similarly prevented controllers from switching from night to daytime operations at NATS’ area control centre at Swanwick, disrupting airport operations across the UK, including Heathrow, Gatwick, Stansted, Luton, Southampton, Birmingham, Cardiff and Glasgow.

The independent expert investigation into that 2013 failure found that NATS’ response had overall been sound and concluded that it was unreasonable to expect NATS to have predicted this failure and the complications with restoring the system and hence the significant impact upon service delivery.

In the wake of the Friday’s disruption, Deakin insisted that the air traffic control systems used by NATS are robust and have contingency built in to them so that if a problem occurs, it can be identified quickly and resolved.

“Our contingency plans worked as they should have done yesterday (Friday 12 December) and allowed our complex systems to be fully back up and running after 45 minutes,” he said in a statement. “Safety was not compromised at any time but we do sincerely apologise for the delays and inconvenience caused to passengers and our airport and airline customers.”

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