LONDON: Britain’s air traffic control operator NATS said Friday that a software defect caused an outage that disrupted hundreds of thousands of passengers last week, resulting in about 2,000 flight cancellations and days of travel chaos.
The disruption cost airlines millions of pounds as they worked to reposition aircraft and crews and provide refunds to affected passengers.
NATS CEO Martin Rolfe said the outage was not related to a similar incident in 2023 and was not caused by military intervention, as some media reports had suggested. He also said passenger safety was never compromised.
“This was a software issue in a specific part of our flight data system, that we have traced to a small subsection of coding,” Rolfe said. “The issue has been identified and mitigation is in place while a permanent fix is safety tested and deployed.”
Transport Minister Heidi Alexander, who last week ordered NATS to provide a report on the incident and requested an independent review by the Civil Aviation Authority, described the disruption as “completely unacceptable.”
“We need to urgently understand why this issue was not discovered and fixed before it caused chaos,” Alexander said in a statement. “It is crucial that our national infrastructure is fit for the future.”
The latest incident followed a major NATS shutdown in August 2023 that caused widespread travel disruption and cost airlines about £100 million ($136 million). Another technical problem at NATS in July 2025 resulted in around 150 flight cancellations.
Ryanair, Europe’s largest airline, has repeatedly called for Rolfe to resign following the 2023 failure.
According to NATS, the latest incident was triggered when an aircraft requested an identification code while the system was processing a higher-priority request, causing the initial request to pause.
“Had the higher-priority request arrived even one millisecond earlier or later, the update would have completed normally,” the report said.
