Air Canada began canceling flights Thursday ahead of a possible strike by its flight attendants that could impact hundreds of thousands of travelers. A complete shutdown of the country's largest airline threatens to impact about 130,000 people a day.

Air Canada said it would reach out via email or text to let customers know if their flights are canceled. The cancellations on Thursday included some long-haul overseas flights. By the end of Friday, the airline expects to cancel 500 flights.

The prospect of a systemwide work stoppage by Air Canada's unionized flight attendants loomed large on Friday with a strike deadline just hours away, despite a government plea for both sides to return to the bargaining table.