The Scandinavian airline SAS has filed for Chapter 11 bankruptcy protection in the United States after a thousand pilots voted to strike Monday. The carrier has canceled half its flights.

European air travel has been particularly chaotic this summer, but there’s been plenty of turbulence here in the U.S. too. More than 2,000 flights were canceled over the July Fourth weekend, and more than 25,000 were delayed, according to FlightAware.

The industry has been struggling with staffing shortages as demand soars to near pre-pandemic levels, and it’s not likely to get better any time soon.

Peter McNally, an analyst with Third Bridge Group, said the aviation industry’s troubles come down to three Cs: capacity, captains and cancellations.

Airlines have been slow to add back capacity because they can’t hire enough captains, or pilots, which leads to cancellations, he said. “It’s a mess, as everyone can see.”

To cut costs during the pandemic, airlines offered early retirement packages to pilots. Plus, training programs aren’t churning out new pilots fast enough.

“This was an emerging problem pre-COVID,” McNally said. “And it’s only accelerated.”

Last week, some Delta pilots held protests at seven airports across the country, calling for higher wages amid increasing overtime.

“This is not a labor-created problem; it’s an airline mismanagement issue,” Capt. Joe DePete, president of the Air Line Pilots Association, International, said in a statement.

Aviation analyst and consultant Robert Mann said the airlines received more than $50 billion in government funding to shore up staffing during the pandemic. But the industry still furloughed or laid off hundreds of thousands of workers.

“The attempt to rehire those folks and get them all qualified and security-cleared at that volume is creating a unique problem,” he said, pointing to wait times for background checks that have stretched up to six or eight weeks, up from one or two.

Airlines for America, a trade group representing major U.S. airlines, pointed the finger at a shortage of air traffic controllers in a June letter to Transportation Secretary Pete Buttigieg.

The Federal Aviation Administration said in a statement there is no “system-wide” shortage of air traffic controllers, though there have been isolated staffing issues at a few locations.

“Numerous factors are contributing to air travel delays and cancellations. The No. 1 cause for delays and cancellation of flights by airlines is convective weather in Florida. Second is demand for travel to Florida.”

Staffing shortages of this nature are likely to persist for some time, said Henry Harteveldt, a travel industry analyst.

“After years of training, you have to submit your application, go through background checks that include a security check, pass drug tests and the interview process and more,” he said.

Harteveldt said it could take until 2025 for staffing levels to catch up — unless a slowing economy cuts the demand for travel.