NATS Fails Again and Leaves 2,000 Flights Grounded

NATS lost its flight-processing system for four hours on 8 September, and more than 2,000 flights were cancelled across the UK. Heathrow filled with people sitting on the floor. Transport Secretary Heidi Alexander told MPs the fault was not unavoidable.

It was the company’s third major technical fault in three years. Industry estimates put about 330,000 travellers in the mess. The Civil Aviation Authority said most of them will not see a cash payout.

A Four-Hour Fault Cancelled 30 Percent of Tuesday’s Flights

The computers failed in the early afternoon, and the network did not catch up that night. Aviation analytics firm Cirium counted 1,750 cancellations on Tuesday, 8 September, from 5,800 scheduled UK flights, about 30 percent of the day’s plan against a normal 1 to 2 percent. Cirium logged another 327 cancellations on Wednesday, about 5 percent of that day’s schedule, taking the two-day total past 2,000.

Heathrow took 541 of Tuesday’s cancellations. British Airways, whose main hub is there, said the NATS issue forced it into cancelling almost 550 flights and hit more than 85,000 customers. Ryanair said it cancelled 260 flights, affecting 48,000 passengers, and put its losses at £3 million ($4 million). Gatwick, Manchester, Birmingham and Stansted were in the same pile-up.

WHO CANCELLED WHAT

Industry estimates split those 330,000 people into more than 155,000 whose flights were cancelled and more than 180,000 who were delayed. Jeanette Clement, trying to reach New York from Heathrow Terminal 5, never left England. “I’ve never seen chaos like that at an airport,” she said, after sitting on the floor with other solo travellers as rumours moved faster than the boards.

Stairs and lifts were taped off. Check-in desks shut. Baggage screens went dark, and people walked belt to belt looking for bags that had already been unloaded from aircraft that were going nowhere. Overhead speakers told them to keep receipts.

Swanwick Has Now Failed Three Times in Three Years

NATS, formerly National Air Traffic Services, runs UK airspace from two area centres. The flight-processing kit that failed sits at Swanwick in Hampshire. Rolfe told Alexander the 8 September outage was a technical issue at that site. Prestwick in Scotland still handles other traffic, but the software that reads flight plans for the country is concentrated at Swanwick.

NATS said this fault was not the same as the crashes in 2023 and 2025. Rolfe also said he did not believe the company had ever seen an incident happen more than once. Airlines UK, which speaks for UK carriers, still called it the third major system failure in three years, and NATS apologised in those terms.

THE THREE SWANWICK FAILURES

1. 28 August 2023: A valid flight plan with duplicate waypoint codes hits the FPRSA-R processor. Primary and backup units drop into maintenance mode in 20 seconds. Automatic planning falls from about 800 plans an hour to about 60. More than 700,000 passengers are caught on a bank holiday.
2. 30 July 2025: A radar-related software fault at Swanwick blanks controller screens. NATS switches to a backup in about 20 minutes and throttles traffic. More than 150 flights are cancelled, most of them around Heathrow.
3. 8 September 2026: The flight-processing system fails at 13:46 BST. Engineers name the system at 15:25, put in a fix at 16:40, and declare it resolved at 19:30. Alexander described the outage as four hours. Cirium’s two-day cancellation count still ran past 2,000.

The 2023 review found that both the main box and its backup shut themselves to stop bad data reaching a controller. That fail-safe was the point. Manual entry could not keep up, so the country rationed takeoffs. NATS later called that event a one-in-15-million case. Three summers later, Swanwick was back on the incident log.

Why the Screens Coming Back Did Not End the Chaos

A restored computer does not put an Airbus back on its stand, or a crew back inside their duty hours. NATS implemented a fix in its flight processing system at 16:40 on Tuesday and said at 19:30 that it was operating normally. By 22:10 it was still warning that recovery had created difficulties for the whole aviation network, from which it would take time to recover.

Heathrow first paused departures around lunchtime, then saw arrivals pile in until the airfield was too full. Incoming flights were turned away to other European airports. The airport suspended arrivals for the rest of Tuesday night even after some departures restarted. On Wednesday it said flights were operating, with knock-on hits as aircraft and crew repositioned, and told people to travel only if their flight was confirmed.

ℹ️ Technical issue
Our operations are stable and we continue to work closely with airlines and airports to support their recovery from the ongoing disruption to their operations. https://t.co/SBXp9l3gUN

— NATS (@NATS) September 9, 2026

Following yesterday's NATS technical issue, flights are operating today, but some disruption may continue as airlines reposition aircraft and crew.
Please check your flight status with your airline before travelling to the airport and only travel if your flight is confirmed to be… pic.twitter.com/DZ2g7GQYkL

— Heathrow Airport (@HeathrowAirport) September 9, 2026

That is why Wednesday still saw 327 cancellations after the computers were “stable.” Hulls sat in the wrong country. Crews ran out of hours. A long-haul that should have turned at Heathrow overnight instead burnt a diversion, a hotel block, and an extra sector. One inbound from Chengdu ended up in Stockholm. A Ryanair passenger spent more than 15 hours in Bergamo after her original flight was pulled. Those hours do not come back when the radar picture returns.

On Thursday morning, 10 September, bags from deplaned passengers were still sitting in Heathrow Terminal 5 arrivals. Rebookings were still dropping people onto other airlines that did not honour their status. The four-hour hole in Tuesday’s plan was still moving through the timetable.

Airlines Own a Stake and Still Pick Up the Tab

NATS is not a distant state agency. The 2001 sale created a NATS public private partnership structure that still holds. The government has a 49 percent government stake and a golden share. The Airline Group holds 42 percent. Staff hold 5 percent. LHR Airports holds 4 percent. The Airline Group’s members include British Airways, easyJet, Virgin Atlantic, Lufthansa and TUI.

Rolfe, marking 25 years of that model on 27 July 2026, wrote that most people boarding a flight would never think about who owns the control service, and that what matters is that it works. Six weeks later his flight-processing system did not.

NATS’s 2026 accounts show statutory profit of £213.0 million and 2.54 million flights handled. The board paid a £69.2 million dividend in the year and another £69.2 million in May 2026. Airlines UK chief executive Tim Alderslade wrote to Alexander after Tuesday’s failure. “The result is a system where airlines pick up the bill for the mistakes of others, while the organisations responsible face little or no financial consequence,” he said. “Accountability should sit where responsibility lies and the Civil Aviation Bill offers the opportunity to address this.”

Ryanair’s chief operating officer, Neal McMahon, went further and called for Rolfe to resign after “repeated mismanagement.” Wizz Air asked for reforms. Ryanair’s chief executive said the cause was the same as the 2023 shutdown. NATS rejects that. The cost still lands in the same place. Carriers buy the hotels, the meals, and the spare aircraft. Then they argue with the regulator about cash.

What Cash Compensation the CAA Has Ruled Out

The CAA said the NATS outage is likely to count as “extraordinary circumstances” under passenger rights rules, so people are “unlikely to be entitled to compensation for delays or cancellations that were directly caused by the incident.” Fixed sums under UK261 run from £220 on a short hop to £520 on a long-haul delay of four hours or more. Those figures apply when the airline is at fault. An air-traffic computer failure is the textbook case where it is not.

That ruling does not wipe the airline’s other duties. If a flight is cancelled, the carrier must still offer passenger rights after a cancelled flight: a refund, a seat on the next available service, or a later flight at the passenger’s convenience. Choose the refund and the care stops. Keep the journey and the airline owes meals, refunds and hotel care while you wait, plus two calls or emails.

WHAT THE CAA SAYS YOU CAN STILL CLAIM

• A refund: The unused ticket back within 7 days if you booked with the airline, longer if you used a third party, and do not pick this if you still want to travel.
• Another seat: The next available routing, including on a different airline if your carrier cannot move you itself.
• Care while you wait: Meals and drinks after 2 hours under 1,500 km, 3 hours between 1,500 km and 3,500 km, or 4 hours beyond that, plus a hotel if you are stuck overnight.
• No fixed cash: The £220, £350 and £520 bands do not apply when the cause is an air-traffic failure the airline could not prevent.

Keep itemised receipts. If the airline does not hand over food or a room, it is expected to repay reasonable costs. Travel insurance may cover delay thresholds that UK261 cash will not. Alexander told MPs there had to be “tough questions about resilience of Nats systems” and added, “We also need to think about consumer redress issues.” The Civil Aviation Bill is where Airlines UK wants that gap closed. It is not closed yet.

Martin Rolfe Has One Week to Explain

Alexander summoned Rolfe on Wednesday morning, then went to the Commons. A spokesperson for Prime Minister Andy Burnham said the government still had confidence in him. Foreign Secretary Ed Miliband called the outage unacceptable. Rolfe has run NATS for 11 years. He said he understood the frustration and that the company took accountability, and he ruled out a cyber attack.

Safety must remain air traffic controllers’ overriding priority, and this morning I have spoken to Nats chief executive, Martin Rolfe, who informed me this outage was due to a technical issue at their Swanwick site. So, while my understanding from Nats is that we can rule out a cyber-attack on this occasion, I do not believe this issue was unavoidable.

Heidi Alexander, Transport Secretary, in the Commons

NATS has seven days to send her an initial report. The CAA has a separate review due in six months. Alexander said she wanted that work to establish cause and to get air-traffic systems able to move people to where they need to be.

WHERE THEY DISAGREE

• Repeat or one-off: Rolfe says each failure is new. Ryanair’s chief executive says Tuesday matched 2023. NATS says the 2026 software path is not the 2023 or 2025 path.
• Avoidable or not: Alexander told MPs she does not believe the issue was unavoidable. NATS has not accepted that wording and is still investigating.
• Who should go: Ryanair and Wizz Air want Rolfe out or the company overhauled. Downing Street said it still has confidence in him.

Safety, NATS said, was not compromised. The people on the floor in Terminal 5 were not in danger. They were also not in New York, Bergamo, or wherever the ticket said. On Thursday morning a pile of luggage from deplaned passengers still sat in Heathrow Terminal 5 arrivals, waiting for owners who were no longer in the building.