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.

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.

Flight attendants are demanding better wages and compensation for unpaid work. Currently, Air Canada only compensates flight attendants for the time they are in the air, but its attendants are seeking pay for the work they do before take-off and after landing, too.