Air Canada reversed course on plans to resume flights on Sunday after the government ordered more than 10,000 cabin crew to end a strike that led to hundreds of cancellations.

The union representing 10,000 flight attendants at Canada’s biggest airline says its members will disobey a government order to return to work , putting plans to restart flights into jeopardy.

After months of stalled negotiations, 10,000 Air Canada flight attendants walked off the job early Saturday morning. The federal government stepped in hours later to order binding arbitration, forcing an end to the strike — or so they thought.