A strike by 10,000 Air Canada flight attendants has been deemed illegal, and workers ordered back on the job. The ruling from the Canada Industrial Relations Board comes after the flight attendants defied an earlier return-to-work order that also told them to submit to arbitration.

The union for 10,000 striking Air Canada flight attendants said Monday they won’t return to work even though the strike, now in its third day, has been declared illegal.