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.

Air Canada has suspended its plan to resume flights and unionized attendants continued picketing on Monday, despite a federal back-to-work order.

Air Canada cancelled more than 600 flights over the past two days in preparation for a potential work stoppage, and Hajdu says it could be days before service returns to normal.