WestJet has cancelled more than 800 flights, upending plans for thousands of passengers as an unexpected strike by aircraft maintenance engineers entered its third day on the busiest travel weekend of the season.

Some 680 workers, whose daily inspections and repairs are essential to airline operations, walked off the job on Friday evening despite a directive from the federal labour minister Seamus O’Regan calling for binding arbitration.

In a news release, the Calgary-based airline said it had cancelled 832 flights as of Sunday as a result of the Aircraft Mechanics Fraternal Association’s “unnecessary work stoppage.”

On Sunday alone, the airline grounded 424 flights. WestJet said it continues to seek intervention and is exploring “every possible avenue for resolution.”

“We continue to hold our view that the current strike serves no purpose other than to inflict maximum damage to our airline and the country,” said airline president Diederik Pen in the news release.

“WestJet is in receipt of a binding arbitration order and awaits urgent clarity from the government that a strike and arbitration cannot exist simultaneously.

“This is something they have committed to address and, like all Canadians, we are waiting.”

The job action comes after union members voted overwhelmingly to reject a tentative deal from WestJet in mid-June and following two weeks of tense talks between the two parties.

A decision from the Canada Industrial Relations Board seemed to affirm the legality of the union’s actions regardless of protocols around arbitration, a process that typically averts work stoppages rather than starting them.

“The board finds that the ministerial referral does not have the effect of suspending the right to strike or lockout,” the tribunal wrote Friday.

O’Regan said the next day the board’s ruling was “clearly inconsistent” with the direction he provided, but later added he respected the body’s independence. He met with both sides Saturday evening.

“I told them they needed to work together with the Canada Industrial Relations Board to resolve their differences and get their first agreement done,” he said in a social media post.

In an update to union members, the AMFA-WestJet Negotiating Committee said the CIRB has ruled that aircraft maintenance engineers are entitled to continue their strike.

Union leaders said they are committed to a negotiated solution, but added it cannot be done alone.

“We hope the ompany will reconsider its standing refusal to respond to our proposals,” the union said.

“Our passengers have been gravely inconvenienced, and we consider the responsibility for this harm to rest exclusively with WestJet.”

Both WestJet and the union are set to reconvene on Sunday.

Meanwhile, travellers across Canada are expressing their frustration over the number of cancelled flights.

Natalie Maxwell, of Hamilton, Ont., was visiting Halifax with some friends for the weekend. She said her group used WestJet to fly to Halifax on Thursday and was scheduled to fly home on Sunday night.

But the return flight was cancelled at 2 a.m. on Sunday, she said.

She had been waiting on hold with WestJet for almost seven hours when she spoke with Global News.

“Very surprising,” Maxwell said.

“I hoped they would try to book us on another airline or try to give us money back immediately, but we basically just have to spend $800 now to get back to Hamilton and hope that they’re going to give us money back.”

Donato Smith was scheduled to travel from Winnipeg to Guadalajara, Mexico, for a doctor’s appointment. The schedule includes layovers in Calgary and Los Angeles.

When he got to the airport on Saturday, he learned his flight to Calgary was cancelled.

After a game of phone tag involving WestJet and a travel agency, he’s grown frustrated.

“(WestJet) says that they’ll book me (on a flight for) July 5, but I need to fly today,” he told Global News on Saturday.

“I need my flight to be today. My doctor is waiting. … It’s not like he’s going to wait for me.”

Trevor Temple-Murray, a resident of Lethbridge, Alta., was at Victoria International Airport trying to get a plane to Calgary so he and his wife and their two-year-old son could go home.

“We’re staying with family, so we can stay here for a bit, but we don’t know,” he said.

“We also looked at trying to rent a car to drive back and the one company that does one-way trips, they’ve cancelled it because of the flights because they’d lose all of their inventory.

“We’ll just have to wait it out.”

Gabor Lukacs, president of the Air Passenger Rights advocacy group, told Global News the strike has been poorly handled by the federal government by “stepping into labour relations where it has no business to step in.”

“From a passenger’s perspective, it would have been much better if WestJet really locked out its employees because passengers would have had more protection,” he said.

“It would have been much better to just let things play out between the union and WestJet, even though it may have, in the short term, inconvenienced passengers, it would have put passengers in a far better position during the time of the lockout.”

Under Canadian air passenger protection regulations, domestic flight cancellations caused by strike action are deemed as being outside of the carrier’s control, Lukacs said.

While airlines are still obligated to rebook passengers, he said they are not obligated to provide meals, accommodations or lump sum compensation.

“That’s a stark contrast compared to the European gold standard, where any kind of labour issue is recognized as something entirely within the airline’s control,” Lukacs said, adding EU rules apply to international flights from Canada.

“If you were travelling from Paris or London back to Canada on WestJet, the European Union gold standard would apply to you and you are owed not only meals and accommodation, but also up to €600 in cash per passenger.”

He said advocates have been calling for changes to Canadian air traveller protections.

“The current air passenger regime in Canada is inferior. It is broken.”

— with files from The Canadian Press and Zack Power, Global News