A technical glitch in the UK’s flight data processing system triggered widespread air traffic disruptions at major British airports on Tuesday, cancelling more than 1,000 flights and delaying hundreds more, according to a report by Reuters.

The fault affected NATS, the UK’s air traffic control provider, and renewed questions about the resilience of the technology supporting Britain’s aviation infrastructure.

NATS said at 1834 GMT that the issue affecting its flight data processing system had been resolved. Earlier, it said that safety had not been compromised.

“Recovery from today’s system issue has taken longer than we had hoped. Our system issue is now resolved, we are operating normally and working as hard as possible to clear the backlog of flights,” NATS said on X.

However, NATS later warned that recovery from the disruption would take time. The provider described the process as a “very complex recovery” that had created difficulties across the wider aviation network.

NATS CEO Martin Rolfe told Sky News that the company had not yet completed its investigation into the cause of the technical problem.

“We don’t have an idea yet of exactly what went wrong,” Rolfe said.

According to flight-tracking website Flightradar24, 1,300 flights to and from UK airports were cancelled on Tuesday. Another 177 flights had been cancelled for Wednesday, with nearly all of them at Heathrow, the country’s largest airport.

Heathrow said at 2019 GMT that arrivals had been suspended for the remainder of Tuesday. Departures had resumed, although the airport said disruption was expected to continue.

Earlier, FlightAware data showed around 490 departures were delayed at six airports, including Heathrow, Gatwick, London City, Luton, Edinburgh and Bristol, as of 1518 GMT. Another 525 arrivals at those airports were either cancelled or delayed.

At Heathrow, 38 of 661 scheduled arrivals had been cancelled or were unable to operate, according to aviation analytics company Cirium. British Airways cancelled 16 of its 333 scheduled departures at the airport.

“The severity of the issue means there will be a significant knock-on impact for customers and colleagues,” British Airways said.

The scale of the air traffic glitch also highlighted the vulnerability of Europe’s tightly scheduled aviation network. Aviation analyst John Strickland said even a relatively short system outage can have severe consequences because delays quickly cascade through airline networks.

“A few hours of outage may on the face of it sound limited but the impact is enormous when a substantial number of airports across the UK are affected,” Strickland said.

Ryanair said around 150,000 passengers had been affected by delays of up to eight hours and that it had cancelled more than 200 flights. The airline also called on NATS CEO Martin Rolfe to resign.

Wizz Air also called for urgent reform of the air traffic control provider. It said airlines, passengers and airports should not continue to bear the consequences of recurring system failures.

“A critical national infrastructure provider should not repeatedly bring the aviation system to a standstill. NATS is simply not fit for purpose in its current form,” Wizz Air said.

Meanwhile, Britain’s aviation regulator said it expected NATS to provide a full report on Tuesday’s incident. The Civil Aviation Authority will then consider whether further action is needed to improve the reliability of the UK’s air traffic control system.

The latest failure comes three years after a flight-plan processing problem caused even more widespread disruption across Britain’s airports. In 2024, the CAA said NATS needed to review its contingency plans for outages after the automatic processing of flight plans malfunctioned. Airline bosses said that incident had cost them more than £100 million in refunds and compensation.

In July last year, a separate radar-related technical issue disrupted flights for more than four hours at major airports in London and elsewhere, including Heathrow.

The latest air traffic glitch has therefore renewed scrutiny of the technology, resilience and contingency planning underpinning Britain’s critical air traffic control infrastructure.

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