VANCOUVER, British Columbia (AP) — Flight attendants with WestJet, Canada's second-largest airline, went on strike Sunday in a dispute over pay.

The Canadian Union of Public Employees, which represents the 4,400 cabin crew at the airline, announced the strike on its Facebook page. WestJet confirmed the strike and canceled 495 flights Sunday, according to FlightAware, snarling travel plans in Canada in the middle of a three-day weekend. The airline said Sunday that the strike led to travel being canceled for 250,000 travelers.

A key issue in the dispute is how flight attendants should be paid for duties performed while still on the ground. The union said some of that work is unpaid, while the company said its staff was indeed compensated, citing pay through a “credit hour” system rather than an hourly rate.

“We presented a proposal that would have set a new standard for cabin crew in Canada, making WestJet the only airline to offer an hourly rate covering all time before and after flights, plus a double-digit wage increase in year one among other priorities the union raised,” said Alexis von Hoensbroech, CEO of the WestJet Group. “Unfortunately, it wasn’t accepted.”

The airline's proposal included a 13% wage increase in October, increases of 2.5% each January for the next three years, retroactive wage payment to last January and additional pay for all hours worked, which is equivalent to another 12% of salary increase, according to WestJet. The proposal also boosted other benefits such as meal per diems, vacation allowance and maternity leave.

Alia Hussain, president of the union chapter that represents the cabin crew, said negotiators “tried until the very last minute to get a fair deal that recognizes the value of the work cabin crews do.”

“WestJet’s offer did not go far enough," Hussain said.

Both sides said they were willing to resume negotiations to reach an agreement.

Meanwhile, travelers whose flights were canceled struggled to find accommodations or alternate flights.

Keavin Ly, a systems administrator for an animation studio, was stuck in Squamish, British Columbia, with his girlfriend after the couple spent the week rock climbing. They were supposed to fly back to Los Angeles on Sunday morning. The airline offered to reschedule their flight for Aug. 4, but they're scrambling to figure out where to stay between now and then.

“Inconveniently, our Airbnb and car rentals are done, and everything’s booked,” said Ly, 29. They were entertaining the idea of sleeping in the back of a friend's rental car, he said.

Ly had planned to take time off from work to watch a friend compete in a national billiards competition, but now he fears he'll miss it. And his girlfriend will miss shifts as a nurse, he said.

“We’re pretty much at the behest of the airline striking a deal, the cabin crew with WestJet, but all in all I hope they get what they’re looking for and they deserve to get compensated more," Ly said.

The airline said it could not operate any of its scheduled flights on Boeing 737s or 787s, and travelers will be refunded or reaccommodated. WestJet said it would contact people who reserved with them directly via email, while those who booked through a travel agent or third-party platform should reach out to them.

WestJet Encore flights?operated?on a Q400, as well as code-share flights?operated?by airline partners, remain unaffected.?

Canada’s Minister of Jobs and Families, Patty Hajdu, called the strike “a disappointing development.”

“A strike or lockout does not mean an agreement can’t be reached; the expectation is that parties can and should come to an agreement at the bargaining table,” Hajdu said in a statement. “The federal government will always maintain that the strongest deals happen at the table. Canadians are counting on them to put their best efforts forward to reach a deal at the bargaining table.”

Last August, when Air Canada flight attendants went on strike over a similar issue, stranding more than 100,000 travelers during peak travel season, Hajdu directed Canada’s labor board to order them back on the job.

The union defied the order, forcing Air Canada back to the bargaining table where the parties hashed out a tentative deal. That work stoppage lasted three days before the sides came to an agreement.

WestJet caught the union off guard by publicly releasing its offer to the flight attendants, said John Gradek, a faculty lecturer on aviation management at McGill University in Montreal.

“This is a bargaining strategy on the part of WestJet to intimidate the union,” said Gradek. “I don’t think the union is happy this has gone public. Right now, the union is kind of trying to figure out what the next steps are going to be. The WestJet offer forces the union to come back to the table and get very specific.”

Gradek estimates the dispute is costing WestJet between Canadian $10 million and $15 million (U.S. $7.13 million and $10.69 million) a day.

Gradek doubts the dispute will last a week. He expects the federal government will give the two sides another day or so before intervening but isn’t sure the government will order the union back to work.

“They may try a different strategy,” he said. “They may want to sit in on the negotiations themselves.”

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Associated Press writer Bernard Condon contributed to this report. Bussewitz and Condon reported from New York.