Summer travelers are facing uncertainty as the clock winds down on a possible strike by Air Canada flight attendants, which the airline said would force it to cancel almost all of its scheduled flights as soon as Saturday.

Air Canada's flight attendants were poised to strike on Saturday as the carrier cancelled hundreds of flights impacting more than 100,000 passengers ahead of a threatened work stoppage that could shut down service.

Air Canada said that more than 623 flights had been cancelled by Friday evening, affecting more than 100,000 people.