The Canada Industrial Relations Board has declared a strike by 10,000 Air Canada flight attendants illegal and ordered them back on the job after they ignored an earlier order to return to work and submit to arbitration.

The Canada Industrial Relations board ordered the flight attendants union to call off the job action by midday.

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,