A software defect within a specific part of the UK’s air traffic control flight data system caused an outage that triggered the cancellation of over 250 flights at Heathrow and Gatwick airports on September 19, 2026. The fault was traced to a small subsection of coding that delayed an identification code request when interrupted by a higher-priority activity, according to an internal NATS report.
Today’s disruption adds to the widespread impact experienced last week, when similar technical issues forced around 2,000 flight cancellations across the UK’s busiest airports, severely affecting hundreds of thousands of passengers and prompting costly repositioning efforts
by airlines.
Statements from NATS and UK Transport Ministry
Martin Rolfe, CEO of NATS, confirmed the outage was unrelated to the August 2023 air traffic control failure or military intervention and emphasized that safety was not compromised. Rolfe explained: “This was a software issue in a specific part of our flight data system, that we have traced to a small subsection of coding.” He added that mitigation measures are currently in place and that a permanent fix is undergoing safety testing.
UK Transport Minister Heidi Alexander described the disruptions as “completely unacceptable” and called for a thorough investigation. “We need to urgently understand why this issue was
not discovered and fixed before it caused chaos,” she said, stressing, “It is crucial that our national infrastructure is fit for the future.” Alexander has ordered both a NATS report and an independent review by the Civil Aviation Authority.
Previous Disruptions and Industry Impact
This latest outage follows a significant air traffic control shutdown in August 2023, which cost airlines approximately £100 million ($136 million) and caused extensive travel chaos. Additionally, a smaller technical problem in July 2025 resulted in 150 flight cancellations. These recurring incidents have intensified pressure on NATS leadership, with Ryanair publicly calling for CEO Martin Rolfe’s resignation since the 2023 failure.
