NATS outage cancels 2,000 UK flights; transport secretary calls it avoidable

A fault in the UK flight processing system at NATS Swanwick on Tuesday grounded more traffic than a typical storm. By Wednesday evening Cirium had counted nearly 2,100 cancelled flights in and out of British airports, about 1,750 of them on the first day. Flightradar24's Tuesday tally was 1,300. Either number is large enough that passengers were still being rebooked on 10 September.

Transport Secretary Heidi Alexander told the Commons the outage was avoidable. She has given NATS chief executive Martin Rolfe seven days to deliver an internal report and commissioned a separate inquiry by the Civil Aviation Authority. After meeting Rolfe she said a cyberattack could be ruled out. "I do not believe this issue was unavoidable."

Four hours at Swanwick, two days of backlog

NATS runs the two en-route centres at Swanwick in Hampshire and Prestwick in Ayrshire. The glitch sat in the flight processing system at Swanwick. Engineers identified the unit about 90 minutes after the failure began. NATS said the system was restored by 19:30 on Tuesday. The aircraft, crews and slots were not.

Heathrow cancelled 541 flights on Tuesday. British Airways said almost 550 of its own services came out, affecting more than 85,000 customers. EasyJet took the largest airline share, followed by BA, Ryanair, KLM and Eurowings. Delayed departures filled Heathrow's stands. Thirteen arrivals were diverted to other UK and European fields because there was no room to park.

Industry estimates given to Parliament put disrupted or delayed passengers at about 330,000. More than 155,000 had flights cancelled. Another 180,000 sat through delays. Some spent hours on the ground in aircraft that never pushed back. Others slept in terminals at Heathrow, Gatwick, Manchester and Birmingham, and at foreign airports waiting for the return leg.

Wednesday added hundreds more cancellations as airlines towed aircraft back to the right bases and found legal crew hours. Heathrow said flying had resumed but warned that the repositioning would run through the day.

Airlines want a resignation

Ryanair chief operations officer Neal McMahon and Wizz Air UK managing director Yvonne Moynihan called for Rolfe to go. McMahon asked the government to treat chronic NATS failures as a policy problem, not an IT accident. This is the second serious NATS breakdown in three years.

Downing Street, speaking for Prime Minister Andy Burnham, said Alexander still has confidence in Rolfe to produce the week's report. That is a holding line. The CAA review will sit beside it and can recommend structural change that a company paper will not.

The Rail Delivery Group told passengers holding Tuesday or Wednesday tickets to or from the affected airports that they can travel on a new date, use another station, or claim a refund. That is a small patch for people whose problem is a hotel in another country and a missed connection beyond Europe.

What still is not public

NATS has not published the software module, the vendor, or the last change that went into the processing system. Rolfe told BBC Radio 4 that complex systems fail and that the company plans for that. He did not name the failure. Until the seven-day paper and the CAA review do, the public record is a four-hour hole, 2,000-plus cancellations and a minister who has already said the hole should not have opened.

For a country that funnels a large share of long-haul traffic through two London airports, the practical lesson is already visible. A single processing stack at Swanwick can stop 30 percent of a day's UK flights. The next report has to say whether that stack has a live spare, and why it did not take over on Tuesday afternoon.