About 500 flights would be grounded by midnight Friday, and it would take about a week to restore full operations once a labor agreement is reached, the company said.

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.

The union representing 10,000 flight attendants for Canada's largest airline issued a 72-hour strike notice on Wednesday.