NATS Identifies One-Millisecond Software Defect as Cause of September 8 UK Flight Disruption
NATS, the UK's air traffic control provider, has attributed the widespread flight disruptions on September 8 to a previously unknown software defect. Preliminary findings, published on September 18, indicate that a one-millisecond timing window during a manual squawk-code request triggered a legacy software module within the National Airspace System (NAS) to produce corrupted output. This led to controllers losing access to some live flight data at NATS’ Swanwick center, which manages higher-level traffic over much of England and Wales. In response, NATS implemented fallback procedures, including manual coordination and traffic flow restrictions, to maintain safety margins. These measures resulted in over 2,000 flights being delayed, canceled, or diverted, affecting hundreds of thousands of passengers. Full air traffic control operations were restored within approximately six hours, though the passenger impact lasted more than two days.
