After two NATS failures, CAA review will scrutinise its own oversight

The Civil Aviation Authority (CAA) will examine whether NATS is investing quickly enough in its critical systems and can maintain services when those systems fail, following two air traffic control outages in 13 days.

The terms of reference, announced on 25 September, go beyond establishing what happened during the nationwide disruption on 8 September. The review will assess NATS’ plans to renew and replace operational systems, its business continuity arrangements and the effectiveness of the CAA’s own oversight. It will also consider whether recommendations from previous investigations have been put into practice.

Transport Secretary Heidi Alexander said passengers and airlines had been “let down too many times”. She wants the review to establish whether NATS is ready for the future “on investment, on its systems, and on resilience”.

Two NATS faults in 13 days

The 8 September failure delayed, cancelled or diverted more than 2,000 flights. As Advance reported when NATS published its preliminary findings, a previously unidentified defect was triggered during a one-millisecond window in the processing of an aircraft squawk-code request. Air traffic restrictions lasted around six hours, with disruption continuing after the system was restored.

On 21 September, another technical failure at NATS’ Prestwick centre led controllers to restrict traffic across parts of Scotland, Northern Ireland and northern England. NATS says the Prestwick connectivity fault was unrelated to the earlier software defect at Swanwick. The CAA says its review will nevertheless be informed by the second incident.

The immediate causes may be different, but both events raise questions about how much traffic the network can handle when a system degrades, what backup arrangements are available and how quickly normal capacity can be restored. The review will examine international practice on resilience and recovery as well as NATS’ own plans.

Earlier lessons under examination

This will not be the first independent review of a major NATS outage. The investigation into the August 2023 flight-planning failure made recommendations on software assurance, contingency capacity, investment and regulation.

The CAA’s latest published progress update classified many of those actions as complete or incorporated into routine oversight. It also recorded difficulties recruiting specialists for resilience oversight, while recommendations concerning investment incentives were being addressed through the next NATS price-control process. The new review offers an opportunity to test whether changes made since 2023 have improved the system’s performance during disruption.

The CAA will hear from NATS, airlines, airports, passenger groups and other stakeholders. An independent challenge panel will scrutinise the work. An initial report is due by the end of January 2027, with the final report to be delivered by 8 March 2027.