Nats resorts to fail-safe manual process after technical hitch

Nats, the UK’s national air traffic control system, experienced a flight planning issue which affected the system’s ability to automatically process flight plans. This meant that flight plans had to be processed manually.

Although the technical issue affecting Nats’ flight planning system were identified and remedied within a few hours, the delay caused major travel disruption across airlines. The problems were acknowledged at 12:10 yesterday (28 August) and were resolved by 15:15.

Juliet Kennedy, operations director at Nats, said: “The issue we had earlier meant our automated system which provides controllers with details of every aircraft and its route wasn’t working. Instead, to manage safety, we had to limit the number of flights we could manage. Our teams worked hard to resolve the problem and I’m pleased to say it was fixed earlier this afternoon. However, it will take some time to return to normal.”

The knock-on effect of the technical issue has caused major disruption to airlines and holidaymakers, many of whom were due to fly back to the UK after the August bank holiday weekend.

On its website, BA said: “While NATS has now resolved the issue, it has created significant and unavoidable delays and cancellations. If you are due to fly with us on Tuesday 29 August, please do not travel to the airport without checking the status of your flight, as it may be delayed or no longer be operating.”

Speaking on the BBC Today programme, Doug Maclean, managing director of DKM Aviation Partners, who worked for 39 years in Air Traffic Control operational, said that it is very rare for the system to fail, even though it is very complex.

“They are very well tested before any changes are made it it,” he said. When asked about the disaster recovery plan, Maclean said that there are backup systems and the air traffic system was never offline during the technical failure, adding: “The airspace never closed. There was traffic moving all the time.”

According to Maclean, what the operations team did during the problem was “very a sensible precaution”. He said that they knew there were issues with data flowing into the system and between air traffic control centres as quickly as it normally would and that they took the decision to enter the data manually.

“It’s actually a testimony to how good the systems are that we can run huge volumes of traffic through the system every day and not experience delays,” he said, adding that this represents a big change from 10 to 15 years ago where, according to Maclean, the system was far less robust.

For instance, on 17 December 2014, Richard Deakin, who was then CEO of Nats, gave evidence to a parliamentary committee looking into a failure of the system that occurred on December 14, which resulted in approximately 150 flight delays and a further 20 flights diverted away from UK airspace. Similar to the statements from Nats regarding the latest technical issue, at the time, Deakin said that air traffic controllers resorted to manual intervention.

“Effectively, the system failed in a degraded mode where the controllers did not have all of the tools available to them that they would normally have, which meant that we had to limit the flow through the airspace,” he said.

The 2014 failure was due to a bug in legacy code developed in the 1990s. While it is too early to know with certainty the root cause of this latest technical issue Nats has experienced, it is unlikely that it was caused by a cyber attack on the system, although this has yet to be ruled out.