A complete shutdown of Air Canada is looming if the union representing the flight attendants of the country’s dominant air carrier and the airline fail to reach an agreement within hours.

Their union says one of its core demands, to receive pay for groundwork, is unlikely to be introduced in arbitration. The airline began canceling flights ahead of the potential strike.

Mark Nasr, Air Canada's chief operations officer, said that cancellations would go from "several dozens" on Thursday, to some 500 by the end of Friday, to the airline being "completely grounded" at the start of the strike on Saturday, in the absence of a resolution.