Union leaders warn the government against using back-to-work powers as WestJet flight attendants poised to strike.

The Canadian Union of Public Employees Local 8125 gave the airline notice early Thursday morning, the union said in a post on its website.

The union representing 4,400 flight attendants at WestJet has issued 72-hour strike notice, setting the stage for a work stoppage that could ground flights in the middle of a busy…