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.

Ten thousand Air Canada flight attendants represented by the Canada Union of Public Employees are on the verge of a strike this weekend, threatening to

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.