Air chaos warning as expert warns tiny errors can trigger UK flight failures

A tiny software error or an anomalous piece of data could bring a critical air traffic control system crashing down, an expert has warned after fresh chaos hit flights across Britain. Josh Piper, product manager at Datactics, said increasingly complex systems could fail when they encountered extremely rare scenarios their software had not been designed to handle.

His warning came after a technical problem at the National Air Traffic Services (NATS) control centre at Prestwick in Scotland disrupted flights across Scotland, Northern Ireland and northern England on Monday. Mr Piper said: “What it looks like we are seeing is effectively error-handling issues with software, new data that software logic hasn’t been designed to handle, causing the software to fail.” The latest problem was fixed by NATS, but the disruption continued as airlines and airports dealt with the knock-on effects of flight restrictions.

Manchester, Belfast International, Edinburgh and George Best Belfast City airports were among those suffering the most disruption, according to aviation analytics company Cirium.

NATS said airports south of Manchester, including those in and out of London, were “broadly unaffected”.

Mr Piper said such failures could be exceptionally rare but still inevitable when systems process vast amounts of data over long periods.

He said: “These appear to be very niche edge cases with the previous incident not occurring in more than 15 million flight plans across 5 years. But as ever with the law of large numbers, given enough time, these kinds of exceptions will happen.”

The expert said the answer was not necessarily to replace entire systems but to ensure software could recognise and contain unusual data without causing the wider network to fail.

Mr Piper said: “The ultimate resolution will be introducing software error handling that can surface these issues and not cause the whole system to fail.”

He also suggested artificial intelligence could eventually help engineers make critical software more resilient by identifying potential failure scenarios.

Mr Piper said: “I would not be surprised if AI could help to make the software system more robust. I would certainly be looking at employing it to assist.”

His comments come just two weeks after a separate NATS software failure caused more than 2,000 flights to be cancelled in and out of the UK.

A report published by NATS on Friday found that a software defect in the National Airspace System was behind that incident.

The system allocates codes that allow air traffic controllers to identify aircraft on radar, and the defect resulted in flight cancellations.

NATS has stressed that Monday’s disruption was unrelated to the previous software failure.

But Mr Piper pointed to a 2023 incident which demonstrated how an apparently minor data problem could have major consequences.

He said: “There was an incident in 2023 that has been fully diagnosed and published. A flight plan contained two waypoints with identical names (4,000 miles apart).”

The system was unable to handle duplicate waypoint names, causing both the primary and backup systems to fail safely rather than risk passing incorrect information to controllers.

Mr Piper said this forced a return to manual flight planning while the problematic data was identified and removed.

He said: “The most recent incident appears to be caused by data again, although I expect there will have to be a similar investigation before we know the full details.”

One possible line of investigation is whether the flight plan of a military aircraft introduced anomalous data, although Mr Piper said this was disputed.

Meanwhile, the latest failure has prompted renewed anger from airlines.

Ryanair chief operations officer Neal McMahon said NATS chief executive Martin Rolfe should stand down, claiming more than 25,000 of its passengers were expected to be affected.

Mr McMahon said: “Martin Rolfe has presided over repeated system failures, repeated passenger disruption and repeated failures to deliver an effective back-up system.”

He added: “Enough is enough. Martin Rolfe should resign today.”

EasyJet said the disruption “once again, calls into question the resilience of NATS’ systems”.

British Airways described it as “disappointing” that some customers faced disruption after “yet another technical fault” involving NATS.

The UK Government owns 49 % of NATS, making it the largest shareholder and giving it a veto over key decisions.

Transport Secretary Heidi Alexander said: “I know this will be deeply frustrating for passengers after the previous issue.”