Flight chaos caused by millisecond software defect, says air traffic control body

An air traffic control failure that sparked widespread travel chaos earlier this month was caused by a "software defect" affecting the system underpinning UK air space management, the national air traffic service Nats has said.

The failure led to more than 2,000 flights being cancelled and hundreds of thousands of passengers affected, with some sleeping on airport floors or getting stuck overseas.

"You can fly to almost anywhere from almost any airport at almost any time. If that stops, even for a moment, then you get huge disruption.

Transport Secretary Heidi Alexander called the disruption "completely unacceptable", while industry body Airlines UK is writing to Nats to demand immediate compensation for costs incurred.

There has also been anger from passengers about how much support they got from airlines, and about the fact that they are unlikely to be entitled to compensation because the regulator judges the situation was extraordinary circumstances.

The defect occurred at 10:00am on 8 September, but it did not become apparent this was a serious problem for another two and a half hours.

Flights in and out of the UK's main airports were affected, including Heathrow, Gatwick, Luton and Glasgow.

Mr Rolfe apologised to those affected by the disruption, saying Nats was "devastated".

"It's clear we need to urgently understand why this issue was not discovered and fixed before it caused chaos," Alexander said, adding that a Civil Aviation Authority review was underway.

In 2023, a computer shutdown over the August bank holiday weekend caused chaos for 700,000 passengers.

Tim Alderslade, chief executive of Airlines UK, said: "Once again, it is passengers who have suffered and airlines who have picked up the pieces - and the tab - of an ATC [Air Traffic Control] system failure, while Nats itself faces no real consequences."

Alderslade also said Airlines UK was writing to NATS "to demand immediate compensation for the costs incurred and a credible plan to improve resilience."