Canada’s biggest airline is poised to start canceling several dozen flights Thursday ahead of a weekend lockout of flight attendants that threatens to throw travel plans for tens of thousands into chaos during the peak summer season.

Air Canada said it will gradually suspend operations over three days, ending with “a complete cessation of flying by Air Canada and Air Canada Rouge” on Saturday, when the lockout is scheduled to begin. Air Canada opted to temporarily halt all flights after a flight attendants union earlier this week voted overwhelmingly to strike.

The cancellations could have ripple effects across air travel, based on the size of Air Canada’s footprint in the industry and its connections to the US and broader international travel.

Air Canada warned that once the lockout be

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