The UK's National Air Traffic Services said a software defect caused the air traffic control failure that disrupted travel earlier this month, according to BBC reported. The outage led to more than 2,000 flight cancellations and affected hundreds of thousands of passengers, with flights in and out of Heathrow, Gatwick, Luton and Glasgow among those hit.

NATS said the defect occurred in the system that underpins the management of UK airspace and happened in the space of a millisecond, producing corrupted data. Air traffic controllers then had reduced information available, so restrictions were imposed to maintain safety. The incident raised questions about the resilience of NATS' systems and prompted some airlines to question chief executive Martin Rolfe's position.