Over 250 flights were cancelled today, 19 September 2026, at Heathrow and Gatwick airports due to an outage triggered by a software defect in the UK air traffic control system, according to Geo News.
Software Cause and Mitigation Efforts
NATS, the British air traffic control operator, reported the issue stemmed from a software defect within a precise subsection of the flight data system’s coding. NATS CEO Martin Rolfe explained the outage was caused when a request for an aircraft identification code was interrupted by a higher-priority request, which arrived at a timing difference of just one millisecond. He stated, “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 added that mitigation measures are currently in place and a permanent fix is undergoing safety testing and deployment. He denied any safety compromise during the event and confirmed the outage was unrelated to the 2023 air traffic control failure or any military intervention.
Government Response and Investigation
Transport Minister Heidi Alexander described the disruption as “completely unacceptable” and demanded an urgent inquiry into why the defect was not detected and resolved sooner. Alexander emphasized the need for resilient national infrastructure, stating, “It is crucial that
our national infrastructure is fit for the future.” She has ordered the Civil Aviation Authority to conduct an independent review of the incident to assess causes and recommend corrective actions.
Context of Past Disruptions and Industry Impact
This incident follows previous significant air traffic control disruptions, including a shutdown in August 2023 that caused approximately 2,000 flight cancellations and resulted in £100 million in costs to airlines. A smaller technical problem in July 2025 caused 150 cancellations. Ryanair, Europe’s largest airline, has criticized NATS management since the 2023 incident and has repeatedly called for CEO Martin Rolfe’s resignation. The latest disruption has caused millions of pounds in
losses as airlines reallocate crews and aircraft while issuing passenger refunds.
