NATS said on Friday 18 September that a software defect caused the nationwide air traffic control failure on 8 September that disrupted flights at Bristol Airport, according to a preliminary report published today.
The fault occurred in "the space of a millisecond" in the National Airspace System, which manages UK airspace. A code request for an aircraft was paused by a higher-priority message and did not resume correctly, corrupting flight data.
Although the fault only affected the London Area Control Centre, NATS applied UK-wide restrictions for around six hours while the system restarted. Bristol Airport was among the airports hit, with dozens of arrivals and departures cancelled. It took over two days to clear the national backlog.
NATS chief executive Martin Rolfe said the fault has been identified and a permanent fix is being safety-tested. He confirmed it was unrelated to the 2023 outage and dismissed claims a military aircraft was involved, a claim the Ministry of Defence had already denied. "At no point last week was safety in question," he said.
The BBC and the Guardian reported that ministers said the report leaves questions unanswered over why the defect was not caught sooner. Passengers are unlikely to get compensation, as regulators judged the disruption extraordinary circumstances.
What this means for your journey: with a fix still being tested, occasional delays remain possible. Check your flight status before setting off, and see our Bristol Airport parking guide for the latest advice.