Military aircraft blamed for UK air traffic control outage affecting 2,000+ flights

On Tuesday, the National Air Traffic Services system that manages British airspace simply stopped working. For four hours, nothing moved. More than 2,000 flights were cancelled. Hundreds of thousands of passengers found themselves stranded—some sitting in aircraft on tarmacs, others learning their flights had been diverted to airports across Europe, a few ending up in Germany when UK runways became unreachable. The cause, according to people briefed on the incident and reported by the Financial Times, was a flight plan submitted by a UK military aircraft that contained erroneous data. That corrupted information entered the Nats system and triggered a cascade failure that the organization could not contain or reverse for hours.

What made the collapse worse was not just the bad data itself, but what Nats lacked when it arrived. Kathryn Leahy, an operations officer at Nats, made calls to airport and airline managers as the system deteriorated. When they asked about backup systems—the redundancy that should catch exactly this kind of failure—she had to tell them there was none. Nats was in the middle of a complete overhaul of its infrastructure. A dedicated backup system would have cost vast amounts of money to build and maintain given the sheer volume of data the organization processes. So there was no safety net. The bad data came in, the system failed, and there was nothing to fall back on.

This was not the first time Nats had failed. In August 2023, a technical problem had delayed nearly 1,600 flights. That crisis prompted the Civil Aviation Authority to issue 34 recommendations for system improvements. Nats said all 34 had been fully implemented. Yet here, three years later, the organization was vulnerable in a different way—not to a technical glitch this time, but to corrupted input and absent redundancy. Martin Rolfe, the chief executive of Nats, ruled out a cyber-attack, which had been the initial suspicion. He said he believed the organization had never experienced the same type of incident twice in 50 years of operation, which meant this would be something entirely new.

The Ministry of Defence said there was no wrongdoing by the military. A spokesperson stated that there was no indication of error on the part of the armed forces, though the statement came with a caveat: the Nats investigation was still ongoing, so further comment would be inappropriate. The military's position was essentially that they had submitted a flight plan according to procedure, and if that plan contained bad data, that was not their responsibility to have caught.

Rolfe was summoned to a meeting with transport secretary Heidi Alexander on Wednesday. Alexander made clear she did not believe the outage was unavoidable. She gave Rolfe one week to explain what had happened and commissioned an independent review by the Civil Aviation Authority. But the pressure on Rolfe extended beyond government. Airlines, particularly Ryanair, called for his resignation. Michael O'Leary, Ryanair's chief executive, said Rolfe was "telling lies to save his own skin" and that his position was "untenable." O'Leary argued that more investigations and reports would not solve the problem—what was needed was accountability and a functioning system.

For the passengers who were affected, compensation was unlikely. The outage qualified as an "extraordinary circumstance" under aviation law, which meant airlines could not be held liable for the disruption. Hundreds of thousands of people had their travel plans destroyed, some had sat in aircraft for more than four hours with no information about what would happen next, and some had been forced to land in foreign countries. But the law offered them no recourse. The system had failed, the backup did not exist, and the cost of that failure fell entirely on them.