National Air Traffic Services suffered a second significant technical failure within a fortnight on 21 September, triggering flight cancellations and delays across Scotland, Northern Ireland and northern England. The fault at Nats's Prestwick control centre prompted British Airways and easyJet to cancel services, with a total of 24 flights cancelled across UK airports according to analysts Cirium, though many services continued to operate.
The disruption marks the second major incident at Nats in rapid succession. Less than two weeks earlier, on 8 September, a catastrophic software defect at the operator's London Area Control centre had caused widespread chaos across the UK aviation network. That earlier outage ultimately led to more than 2,000 flights being cancelled or failing to take off by 10 September, according to figures cited by a national broadcaster.
The Prestwick fault on 21 September was caused by a Flight Data Processing System failure, restricting Scottish-controlled airspace capacity by 60 per cent. Nats confirmed the two incidents were unrelated, with the operator stating that airports south of Manchester remained broadly unaffected, though flights heading north and departing from Scottish airports faced delays.
What caused the earlier September outage?
The 8 September incident was traced to a software defect in Nats's flight data system. Nats chief executive Martin Rolfe described the failure as a software issue in "a small subsection of coding", according to reporting on the preliminary investigation findings published on 18 September. The fault began at 13:25 at the London Area Control centre and was not caused by any incorrect actions by staff, Nats's preliminary report confirmed.
What have airlines said?
EasyJet expressed frustration at the repeated disruptions, with a spokesperson stating:
A Nats air traffic control system failure in its Prestwick centre is causing delays to flights with some unable to operate. This, once again, calls into question the resilience of Nats's systems and demonstrates the need for firm actions to prevent these repeated failures.
British Airways similarly criticised the situation, with a spokesperson saying:
Yet another technical fault with Nats means some of our customers are likely to experience disruption to their travel plans today. This is disappointing, and while it is an issue that is entirely out of our control, we're doing everything we can to limit the impact on customers and are keeping them updated.
A Nats spokesperson responded to the 21 September incident by saying:
Our engineers are continuing to investigate the issue at our Prestwick centre in Scotland. Airports south of Manchester are broadly unaffected, however flights heading north and flights departing Scottish airports are now subject to some delay. Passengers should check with their airlines. This is unrelated to the issue two weeks ago. We apologise for the disruption.
What has the government said?
The repeated failures have drawn government scrutiny. Transport Secretary Heidi Alexander told Parliament she had ordered an independent investigation by the aviation watchdog into the Nats system failure and said the incident was avoidable. This announcement came on 18 September, ten days after the major outage.
The government's decision to order an independent investigation reflects growing concern about the resilience of the UK's air traffic control infrastructure. The 8 September outage represented the third major disruption in three years, intensifying pressure on Nats to prevent future incidents.
What happens next?
The aviation watchdog's independent investigation ordered by Transport Secretary Alexander represents the formal next step in examining the systemic issues at Nats. No hearing date has yet been set for the investigation. Nats has committed to publishing further technical analysis following its preliminary report on the 8 September incident, which was issued on 18 September.
Key Facts
- A second Nats technical failure on 21 September disrupted flights across Scotland, Northern Ireland and northern England, with 24 cancellations reported
- The earlier 8 September outage at Nats's London control centre caused over 2,000 flight cancellations, affecting hundreds of thousands of passengers
- Both incidents were caused by software defects in Nats systems, with the September fault traced to a small section of code
- Transport Secretary Heidi Alexander has ordered an independent aviation watchdog investigation into the failures
- The repeated disruptions have intensified scrutiny of Nats's operational resilience and prompted calls from airlines for systemic improvements
