NATS preliminary report traces September airspace disruption to flight data software bug

NATS, which runs air traffic services across the UK, has put out a preliminary report on the disruption that hit passengers earlier this month. The transport secretary asked for it; a fuller account is due within 60 days of the event.

The 8 September incident came down to a software fault in the National Airspace System, the platform that manages UK airspace, according to the report. The code in question handles squawk codes, the identifiers controllers use to spot flights on radar once they are airborne. Those are normally assigned automatically, but this code covers manual requests.

The fault appeared while one such manual request was being handled, the preliminary findings say. A message for a higher-priority activity came in and paused the request. When processing picked up again, the bug produced a corrupted output.

A formal major incident was declared at 12:32. NATS called the problem a software issue confined to a narrow section of code, and said it has been identified. Mitigation is in place while a permanent fix goes through safety testing before deployment.

NATS said the outage was not connected to the significant system disruption of August 2023, and rejected suggestions that military action played a part. The full report is still to come.