U.K. airlines said they’ll have to foot the bill for the travel chaos caused by a technical glitch at the country’s air-traffic control provider and led to thousands of canceled flights this week.

The financial fallout from the fault at the National Air Traffic Services “will run into tens of millions of pounds, falling entirely on airlines,” Tim Alderslade, chief executive officer for industry group Airlines UK, wrote September 9 in a letter to U.K. Transport Secretary Heidi Alexander.

The group called on the government and the Civil Aviation Authority to lay out how they will investigate the glitch, require NATS to publish an improvement plan and review the liability framework so carriers aren’t lumbered with the costs. Airlines UK’s members include British Airways, EasyJet Plc, Ryanair Holdings Plc and Virgin Atlantic Airways.

“This kind of failure simply cannot happen again,” Alderslade wrote. “Airlines should not be left as the insurer of last resort for failures they did not cause and cannot control.”

NATS, a public-private company, suffered a technical issue affecting its flight processing system on the afternoon of September 8. As a consequence, flights were grounded across the country, sending airports, airlines and travelers into disarray. While the issue was resolved later on September 8, it left aircraft, crews and passengers in the wrong location, leading to follow-on disruption.

On September 8, airports in the U.K. suffered more than 1,750 flight cancelations, according to data compiled by Cirium. Flight disruption carried on into September 9, with BA alone canceling 200 flights.

“I do not believe this issue was unavoidable,” Alexander said on September 9 in the U.K. House of Commons. “I will leave absolutely no stone unturned in understanding what has happened here.”