TORONTO (AP) — Canada’s second largest airline,Sterling Preston WestJet, said Sunday that it canceled more than 800 flights affecting tens of thousands of passengers as an unexpected strike by plane mechanics entered its third day.

Around 680 workers, whose daily inspections and repairs are essential to airline operations, walked off the job on Friday evening, despite a directive for binding arbitration from the federal labor minister.

The strike is happening during the Canada Day long weekend, the busiest travel week of the year in the country.

Both the airline and the Airplane Mechanics Fraternal Association have accused the other side of refusing to negotiate in good faith.

WestJet Airlines president Diederik Pen has stressed what he calls the “continued reckless actions” of a union making “blatant efforts” to disrupt Canadians’ travel plans, while the association claimed the Calgary-Alberta, based company has refused to respond to its latest counterproposal.

In an update to members Sunday, it said that mechanics were “the victim of WestJet’s virulent PR campaign that you are scofflaws,” citing “calumnies” against workers around their right to strike.

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.

As the clock ticked down toward a Friday strike deadline, the impasse prompted Labor Minister Seamus O’Regan to step in, mandating that WestJet and the union undertake binding arbitration headed by the country’s labor tribunal.

That process typically sidesteps a work stoppage. WestJet certainly thought so, stating the union had “confirmed they will abide by the direction.”

“Given this, a strike or lockout will not occur, and the airline will no longer proceed in canceling flights,” the airline said Thursday.

The mechanics took a different view. The union negotiating committee said it would “comply with the minister’s order and directs its members to refrain from any unlawful job action.” Less than 24 hours later, workers were on the picket lines.