Air traffic control chaos affecting 700,000 passengers was made worse when an engineer couldn't log in remotely

• About 700,000 passengers were affected by air traffic control chaos in the UK in August 2023.
• A report found an engineer struggled to log in remotely, meaning it took longer to resolve the issue.

An engineer's login struggles hindered attempts to solve an air traffic control meltdown that affected 700,000 passengers in the UK.

The details were revealed Thursday in a report by the UK's Civil Aviation Authority about the August 2023 travel chaos.

It estimated the event cost airlines, airports, insurers, passengers, and others between £75 million and £100 million ($127 million) — and that about 300,000 people had their flights canceled. Another 95,000 were delayed by more than three hours, and a further 300,000 faced shorter delays.

The incident was caused by a software failure. A single flight plan for a journey from Los Angeles to Paris — passing over the UK — contained two waypoints with the same name.

This confused the automatic flight planning system, causing both the primary and the backup to shut down within 20 seconds.

The system can usually process 900 flight plans an hour during peak periods, but air traffic controllers had to process them manually — reducing its capacity to just 60 an hour, the report found.

It also identified numerous factors that meant it took longer to identify and rectify the problem.

One such factor was that a Level 2 engineer systems expert was on call but couldn't intervene remotely because their login and password "could not be readily verified due to the architecture of the system."

It took the engineer 90 minutes to reach the air traffic control site — just over three hours after the meltdown began.

All the traffic regulations implemented due to the incident were lifted after a total of nine-and-a-half hours.

Delays and cancellations had knock-on effects on airline schedules, causing further issues for the next week. The report estimated that airlines lost £65 million ($82 million) as a result.

The report recommended that NATS, the UK's air traffic control provider, has a Level 2 engineer working on-site during busy travel periods.

Its 34 recommendations include government legislation, requiring airports and airlines to review the support available for affected passengers, and for NATS to provide earlier notices of possible disruption.

UK Transport Secretary Louise Haigh said, "My department will look to introduce reforms, when we can, to provide air travelers with the highest level of protection possible."

A NATS spokesperson said in a statement that it welcomed the report and apologized "for the inconvenience passengers suffered because of this very unusual technical incident. Over the 15 months since this incident, we have worked hard to address the lessons from it, and to ensure this particular issue cannot happen again.

"NATS has implemented most of the 48 recommendations from its own investigation, including "improving our engagement with our airline and airport customers, our wider contingency and crisis response, and our engineering support processes."