An inquiry into the incident in August 2023, which saw 700,000 passengers stranded due to cancellations due to a shutdown of the UK air traffic control's computer system NATS, found part of the issue was an engineer unable to use his password from home to reset the system.

According to the Civil Aviation Authority report, the engineer did not get to their workplace until nearly three hours after the problems started.

"Several factors made the identification and rectification of the failure more protracted than it might otherwise have been," the report said.

"The Level 2 engineer was rostered on-call and, therefore, was not available on site at the time of the failure.

"Having exhausted remote intervention options, it took 1.5hours for the individual to arrive on-site to perform the necessary full system re-start which was not possible remotely."

The impact of the delay lasted days, with some passengers unable to secure replacement flights, and is estimated to have cost airlines $100 million.

After the issue was detected at 8.30am on August 28, it took half an hour for the engineer to be contacted. The engineer was then unable to use their password as the system had crashed, meaning they could not log in remotely.

NATS said it would review its plans to make sure a similar incident did not happen again.