UK Air Traffic Glitch Caused Widespread Flight Cancellations

A preliminary report released on Friday has identified a millisecond-software defect as the cause of the cancellation of over 2,000 flights in and out of the United Kingdom on September 8. The glitch occurred within the National Airspace System, which is responsible for assigning codes that allow air traffic controllers to identify flights on radar.

NATS, formerly known as National Air Traffic Services, stated that the defect, not human error, led to the decision to cancel flights. This incident caused significant disruption for hundreds of thousands of travelers, stranding passengers for hours and delaying the resolution of the chaos for days.

NATS Chief Executive Martin Rolfe described the issue as a "software issue in a specific part of our flight data system, that we have traced to a small subsection of coding." He confirmed that mitigation measures are currently in place while a permanent fix undergoes testing and deployment. Rolfe reiterated apologies for the disruption and emphasized that the incident did not result from any incorrect actions by military or civil operators. He also noted that this event is unrelated to previous outages in late 2023 and a radar issue in July of the same year.

In response to the disruption, U.K. Transport Secretary Heidi Alexander met with Rolfe and requested a comprehensive investigation to ensure lessons are learned. "While I am pleased to see that the safety of passengers was protected, it’s clear we need to urgently understand why this issue was not discovered and fixed before it caused chaos," Alexander stated.

Alexander has tasked the Civil Aviation Authority with conducting an independent review to verify NATS’ findings. This review will also examine NATS’ investment plans for future resilience and assess regulatory accountability. The U.K. government holds a 49% stake in NATS, making it the largest shareholder in the public-private partnership, which also includes airlines, airports, investors, and employees as stakeholders.