Air Canada began canceling flights Thursday ahead of a possible strike by its flight attendants that could impact hundreds of thousands of travelers.

A complete shutdown of the country’s largest airline threatens to impact about 130,000 people a day.  

The airline said in a social media post that nearly 300 flight attendants, “twice as much as usual,” did not report to work Thursday night. 

“This will result in additional cancellations,” the airline said. “We regret the inconvenience to customers.”

Mark Nasr, chief operations officer for Air Canada, said the airline has begun a gradual suspension of Air Canada and Air Canada Rouge operations.

“All flights will be paused by Saturday early morning,” he said.

Nasr said this approach will help facilitate an orderly restart, “which under the best circumstances will take a full week to complete.”

He said a first set of cancellations involving several dozen flights will impact long-haul overseas flights that were due to depart Thursday night. “By tomorrow evening, we expect to have canceled flights affecting over 100,000 customers,” Nasr said. “By the time we get to 1 a.m. on Saturday morning, we will be completely grounded.” 

He said a grounding will affect 25,000 Canadians a day abroad who may become stranded. They expect 500 flights to be canceled by the end of Friday.   

The union representing around 10,000 Air Canada flight attendants issued a 72-hour strike notice on Wednesday. If a deal isn’t reached or the government doesn’t intervene, the flight attendants will begin striking on Saturday, Aug. 16. 

In response to the strike notice, the airline issued a lockout notice.

Nasr said customers whose flights are canceled will be eligible for a full refund, and said the airline has also made arrangements with other Canadian and foreign carriers to provide alternative travel options “to the extent possible.”

“We regret the impact a disruption will have on our customers, our stakeholders and the communities we serve,” Air Canada CEO Michael Rousseau said in a previous statement.

On Tuesday, Air Canada said it had reached an impasse with the union as the two sides remained far apart in contract talks. The union has said its main sticking points revolve around what it calls flight attendants’ “poverty wages” and unpaid labor when planes aren’t in the air, while Air Canada said it had offered a 38% increase in total pay over four years, as well as other benefits.

“Despite our best efforts, Air Canada refused to address our core issues,” the union said in a bargaining update posted online.

The union rejected a proposal from the airline to enter a binding arbitration process, saying it prefers to negotiate a deal that its members can then vote on.