A software defect in the UK air traffic control flight data system caused an outage on September 9, 2026, resulting in significant disruption at London’s Heathrow and Gatwick airports. NATS, the UK air traffic control system operator led by CEO Martin Rolfe, identified the issue as a software fault in a small subsection of coding within the flight data system.
Flight Cancellations at Heathrow and Gatwick Exceed 250
More than 250 flights were cancelled at Heathrow and Gatwick airports due to the outage. British Airways cancelled or diverted over 100 flights, while Ryanair cancelled more than 50 flights, disrupting over 65,000 Ryanair passengers. Irish airports including Dublin were
also affected, with dozens of flights cancelled. FlightRadar24 reported 177 cancellations on Wednesday amid ongoing delays triggered by the disruption.
Technical Cause: Sub-Millisecond Software Timing Error
NATS CEO Martin Rolfe explained the cause as a software issue within the flight data system, specifically a timing conflict where a request for an aircraft identification code was interrupted by a nearly simultaneous higher priority operation. Had the higher-priority request arrived one millisecond earlier or later, the update would have completed normally. This error triggered backup protocols requiring manual flight handovers, reducing system capacity and causing widespread delays.
Passenger Impact and Network-Wide Delays
Passengers faced cancellations and long waits at London airports. Gatwick passenger
Josie Donoghue described the situation as “just an absolute nightmare down there.” The disruption affected UK airports including Liverpool, Birmingham, and Edinburgh, and international flights to Dublin and Napoli were impacted. Airlines had to refund tickets and rearrange crews and aircraft. Arsenal’s football team delayed travel plans due to the disruption. A passenger reported disembarking after waiting three hours on a runway.
Official Responses and Demands for Accountability
Transport Minister Heidi Alexander called the disruption “completely unacceptable” and demanded an urgent independent review by the Civil Aviation Authority to assess aviation infrastructure. NATS CEO Martin Rolfe confirmed the issue had been identified and mitigations implemented while
a permanent fix undergoes safety testing. Ryanair COO Neil McMahon criticized NATS leadership and called for Rolfe’s resignation, stating, “Martin Rolfe has run out of excuses. The ‘software ate my homework’ is not an acceptable explanation.” McMahon also questioned why similar failures persist and demanded government action.
This software defect is unrelated to the 2023 UK air traffic control failure, which cost airlines around £100 million. Disruptions like these cause multi-day recovery periods across the UK aviation network and form part of ongoing challenges to UK air traffic control system reliability.
