UK air traffic control outage cost economy an estimated £33 million, Cyber Monitoring Centre says

A failure of air traffic control systems at National Air Traffic Services (Nats) on 8 September cost the UK economy an estimated £33 million, the Cyber Monitoring Centre (CMC), a non-profit organisation, said in a report published on Wednesday. More than 2,000 flights were cancelled and hundreds of thousands of passengers were affected, and the disruption continued into the following day. Nats said the fault occurred in "the space of a millisecond".

The CMC's £33 million figure covers costs to UK airlines, airports, ground operators and tour operators from cancellations, delays and diversions. Airlines absorbed more than three-quarters of the impact, while Nats lost less than £1 million in route charges on cancelled flights. Including overseas airlines, the CMC put the total loss at between £48 million and £76 million, excluding losses to other non-UK organisations such as airports. The CMC assumed no material external incident-response or system-rebuild costs, because Nats' in-house staff carried out the response and the fix.

The CMC placed the incident in the "lowest impact" category on its five-point scale and said it was caused by a "previously unknown defect in legacy software" and was not malicious. Ciaran Martin, chairman of the CMC technical committee, said it was an accidental technology failure rather than a cyber attack and that safety was maintained throughout. He compared it to the 2024 CrowdStrike outage, saying a fault in a single system can spread disruption and cost across dependent organisations.

Nats' preliminary report found the problem was caused by a software issue rather than "any incorrect actions". A second, unrelated air traffic issue less than two weeks later led to more than 170 flights being cancelled. Nats chief executive Martin Rolfe resisted calls to resign after both incidents, including a call from Ryanair. A Nats spokesperson said it would not comment on the CMC's report, noting that the CAA is conducting an independent review of the 8 September incident.

The split of the loss is the most telling feature of the figure. Nats, the party whose system failed, lost under £1 million in route charges, while airlines carried more than three-quarters of the £33 million. Air traffic control is a shared utility in which the provider's fault is paid for downstream: by carriers that cancel and re-accommodate, and by airports and ground handlers whose operations stall. That asymmetry is what the CMC's CrowdStrike comparison points at, a single system whose failure spreads cost across dependent organisations.

The gap between £33 million for UK parties and £48 million to £76 million with overseas airlines also shows how hard the full cost is to pin down. Foreign carriers and non-UK airports sit partly outside the estimate, so any single headline number understates the cross-border reach of a UK-airspace outage. A "lowest impact" rating on the CMC's scale did not prevent more than 2,000 cancellations, which says something about how the scale measures economic loss rather than passenger disruption.

The next fixed point is the CAA's independent review of the 8 September incident, which Nats has said it is awaiting before commenting on the CMC's findings. That review, alongside the second disruption less than two weeks later and the pressure on Nats leadership, is where questions about legacy software and resilience will be tested against evidence.