A Four-Hour NATS Failure Grounded Nearly a Third of UK Departures

A fault in the system that feeds flight data to Britain’s air traffic controllers disrupted about 2,000 flights across two days this week. The failure at NATS, the UK’s main air navigation service provider, began early on the afternoon of Tuesday, September 8, 2026, and lasted around four hours.

Aviation analytics firm Cirium counted about 2,000 flights to and from UK airports affected on Tuesday and Wednesday, with 30% of scheduled departures grounded on Tuesday alone, Reuters reported. Heathrow, Gatwick, Manchester and Stansted were among the airports hit.

What NATS has said

NATS published a running log of statements as the day unfolded. It first reported a technical issue affecting departures at 1:46 p.m. and identified the fault in its flight processing system shortly after 3 p.m.

Chief executive Martin Rolfe said he took “full responsibility” for the disruption, according to reporting by PA. Ryanair has called for him to resign, while Downing Street said the government still had confidence in him.

British Airways said the fault forced it to cancel almost 550 of its flights, affecting more than 85,000 passengers.

The government orders a review

Transport Secretary Heidi Alexander told the House of Commons on September 9 that Rolfe had traced the outage to a technical issue at NATS’s Swanwick site. She said a cyber attack could be ruled out on this occasion, “but I do not believe this issue was unavoidable.”

She has asked the Civil Aviation Authority to run an independent review and report back within six months. The CAA says it will examine what happened and how well NATS is set up to deliver a resilient service, while NATS itself has been given one week to report on the incident.

Why a four-hour fault takes two days to clear

NATS handles more than 2.5 million flights a year over the UK and the eastern North Atlantic. A flight data processing system is what turns each airline’s filed flight plan into the route, levels and timings shown to every controller who will handle that flight.

When that feed is degraded, controllers can keep working, but each one can safely handle fewer aircraft. The standard response is to cap the number of flights entering busy airspace, which is why NATS kept the airspace open while flow restrictions held departures on the ground.

The fix does not end the disruption. Aircraft and crews finish the day in the wrong cities, some crews run out of legal duty time, and every cancelled rotation removes an aircraft from the next morning’s schedule.

That knock-on effect is hardest at London Heathrow, which runs close to its capacity and has little spare slack to absorb the backlog. The same chain of delays followed a two-hour FAA equipment failure at Minneapolis in August.

Third major UK outage in three years

On August 28, 2023, the NATS flight planning system stopped processing flight plans on a bank holiday Monday. The CAA’s independent review estimated that more than 700,000 passengers were affected, 300,000 of them by cancellations, and made 34 recommendations.

A shorter fault on July 30, 2025, led to 122 cancellations by that evening, according to Cirium data reported by Reuters, and NATS said it had switched to a backup system. NATS has not yet said what triggered this week’s failure.