NATS says software defect caused UK air traffic control outage

London, United Kingdom. A software defect caused last week’s UK air traffic control outage that affected hundreds of thousands of passengers, NATS chief executive Martin Rolfe said on Friday. The disruption resulted in 2,000 flight cancellations and prompted airlines to renew calls for his resignation.

Preliminary findings

Rolfe said the fault was traced to a small subsection of coding in a specific part of the flight data system.

“The issue has been identified and mitigation is in place while a permanent fix is safety tested and deployed,” he said in a statement accompanying NATS’ preliminary report.

He said the shutdown was not related to a 2023 incident that also caused widespread disruption and was not linked to military intervention, as reported by some media outlets. Safety was not compromised, he added.

Government review

Transport minister Heidi Alexander said the disruption was “completely unacceptable” after requesting a report from NATS and ordering an independent Civil Aviation Authority review.

“We need to urgently understand why this issue was not discovered and fixed before it caused chaos,” she said. “It is crucial that our national infrastructure is fit for the future.”

Airline response

Airlines incurred millions of pounds in costs as they worked to restore crew and aircraft positions and refund passengers.

The August 2023 shutdown cost airlines £100 million ($136 million), while a radar fault at NATS caused 150 cancellations in July 2025.

Ryanair, Europe’s largest airline by passengers flown, repeated its call for Rolfe to resign. Chief Operations Officer Neil McMahon said: “Martin Rolfe has run out of excuses. The ‘software ate my homework’ is not an acceptable explanation.”