Thousands of air travelers across the country had their Canada Day long weekend plans disrupted Saturday after WestJet Airlines cancelled more than 350 flights in the wake of unexpected strike action by its unionized mechanics.

WestJet said more than 30,000 passengers were affected by the flight disruptions Saturday, and an additional 250,000 travelers might be impacted if the strike continues through the long weekend.

Hundreds of WestJet mechanics walked off the job Friday evening following a strike notice issued by their union, the Aircraft Mechanics Fraternal Association (AMFA).

On Saturday, travelers were hovering around the WestJet booth in Terminal 3 of Toronto’s Pearson International Airport anxiously waiting to find out if their flights had been cancelled.

Villamor Torres and Mary Jane Herrera came to the airport after struggling to rebook their cancelled flight over the phone. The Toronto couple was looking forward to starting their vacation in the Cayman Islands on Saturday when they received an email at 9:40 a.m. notifying them that their flight was cancelled.

“We’re trying to figure out what to do—we’re in the middle of getting a new flight but they said if we get a new flight they won’t compensate us,” said Ms. Herrera.

At the airport, they were met with more confusion. “They say they’ll get us a new flight but when we ask which one they’re not responding,” said Mr. Torres.

“It’s chaos,” said Amy Morris, who was visiting the country for the first time from Atlanta, Ga., with her family. “We had a hiking trip planned tomorrow in Banff, we lose the entire first day at least…it’s not a great introduction to Canada.”

The family of four were headed to Calgary when they learned of the cancellation while on a connecting flight to Toronto. “We’re getting no information from WestJet at all — they said within a couple of hours we’ll get a reassignment, but we’ve heard nothing,” said Ms. Morris. “It was a last family vacation, the kids are moving out of state, and it was supposed to be our last hurrah.”

Some travelers arriving at Pearson were pleasantly surprised that their WestJet flights had not been cancelled.

“We had no problems with our flight so far,” said Dave Johnson, the President of the Bowling Association of Ontario who was headed to Winnipeg for a national championship with 40 other players. “They’ve checked our bags already… I was thinking they’d have picket lines and be blocking the doors.”

Sean McVeigh, a WestJet aircraft maintenance engineer picketing at Pearson’s Terminal 3 on Saturday, said the strike is an attempt to force the airline to return to a “respectful negotiation.”

McVeigh said the union regrets any inconvenience caused to passengers.

“However, the reason they [passengers] have possibly missed a flight or had to cancel is due to the reason that WestJet is not respectfully sitting down at the table and negotiating,” he said alongside roughly 20 others on the picket line. “We take on a lot of responsibility and we would just like to be appreciated financially,” he said.

WestJet said another 150 flights could be cancelled by the end of the day Saturday if there was no resolution to the walkout.

“We are extremely outraged at these actions and will hold AMFA 100 per cent accountable for the unnecessary stress and costs incurred as a result,” said WestJet Airlines president Diederik Pen in a statement.

The union said WestJet’s “unwillingness” to negotiate made the strike inevitable, and accused the airline of insinuating retaliatory action against union members.

The country’s second-largest airline pleaded for immediate intervention by the federal Labour Minister Seamus O’Regan and Canada Industrial Relations Board.

On Saturday, Mr. O’Regan said he was reviewing a decision made by the industrial relations board to refer a dispute between WestJet and the AMFA for binding arbitration — a process where a third party deliberates on the terms of a collective agreement.

“I will be taking additional steps to protect the interests of the employer, the union and all Canadians traveling over this national holiday weekend,” Mr. O’Regan said in a statement posted on X.

But a new statement later in the day said he respects the authority of the board, which he noted is independent from the government. He intended to meet with the two sides later Saturday, he added.

The airline’s CEO, Alexis von Hoensbroech, blamed the situation on what he said was a “rogue union from the U.S.” that was trying to make inroads in Canada.

Von Hoensbroech said as far as the airline was concerned bargaining with the union had come to an end once the minister directed the dispute to binding arbitration.

“This makes a strike totally absurd because the reason you actually do a strike is because you need to exercise pressure on the bargaining table,” he said. “If there is no bargaining table it makes no sense, there shouldn’t be a strike.”

He added the union had rejected a contract offer that would have made the airline’s mechanics the “best paid in the country.”

Whatever the outcome of the contract dispute, Gábor Lukács, a Canadian air passenger rights advocate says WestJet has a legal obligation to provide passengers with cancelled flights a reasonable and speedy alternative.

“Under the Air Passenger Protection Regulations they need to reschedule you on another airline or buy a ticket from a competitor,” he said, adding that this should be done within the first few hours after a cancelled flight. “If WestJet is not reachable for several hours they are not fulfilling their obligation.”

Passengers who can’t reach the airline or aren’t offered a clear alternative travel plan should proceed to book a flight at their own expense and send WestJet the bill, Lukacs recommended. Most importantly — ”they should document every message and exchange with the airline.”

With reports from The Canadian Press.