More than 10,000 flight attendants are poised to walk off the job around 1 a.m. ET on Saturday, followed by a company-imposed lockout if the two sides can't reach an eleventh-hour deal.

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.