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Britain’s aviation regulator will launch an independent review into the failure of the air traffic control system over the August bank holiday that grounded hundreds of aircraft and left thousands of passengers stranded.
The review by the Civil Aviation Authority comes after an interim report by the National Air Traffic Services (Nats) found that a “logic error” occurred after a part of its system incorrectly processed a flight plan from an airline flying over UK airspace.
Airlines have to submit flight plans detailing their routes and timings to air traffic controllers to minimise the risk of mid-air collisions, including way points or markers along the route. According to the report, Nats’ software found the entry point into UK airspace for the airline but when it looked for the exit point it found duplicate points that corresponded to somewhere else in the world, triggering a “logic error”.
The anomaly forced both the primary and the back-up systems to enter a fail-safe mode, forcing Nats flight controllers to resort to entering flight data information manually.
“This incident was caused by a specific flight plan,” said Nats chief executive Martin Rolfe.
“That flight plan that the airline entered was not faulty . . . However, it presented data to our systems that had never been seen before and it did it in a way that generated a logic error due to the software processing.”
“The airline submitted a perfectly compliant flight plan into their systems; it was our system that didn’t process the flight plan properly,” he added.
Rolfe declined to provide further information on the flight “because it isn’t pertinent to the problem”.
Although duplicate way points do exist, Nats said it was the duplicate, coupled with the specific order in which the way points occurred, that was the issue in this instance.
The agency stressed that at no point was air safety compromised during the incident and that a similar scenario had never previously been encountered by the system over the five years it had been in service. Over that time, the system has processed more than 15mn flight plans.
Nats said it had implemented a solution to avoid any possible recurrence. It is also working with the manufacturer of the software, Austria’s Frequentis, a specialist in providing safety-critical communication solutions, to implement further updates over the coming days.
The outage at Nats on Monday August 28, at the end of a busy bank holiday weekend, was the worst in more than a decade and led to more than 1,500 flights being cancelled on the day, with more on subsequent days as airlines tried to recover their schedules. Airlines, which are on the hook to reimburse passengers, want Nats to cover their costs.
The CAA review will consider issues raised by the failure as well as the response to the incident by Nats. The regulator will set up a review panel led by an independent chair with the aim of reporting back to the transport secretary within three months.
Rob Bishton, joint interim chief executive of the CAA, said that if “there is evidence to suggest Nats may have breached its statutory and licensing obligations we will consider whether any further action is necessary”.
Under the conditions of its licence, Nats has to meet performance criteria or else face financial penalties.
Rolfe declined to confirm whether he would be accepting his full bonus this year, adding “any matters of compensation are for the board to answer”.
He said that his focus was “on leading the team through what’s been a really difficult period”.
