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.

The Canada Industrial Relations Board had declared the strike illegal earlier on Monday and ordered the striking flight attendants back on the job. But the union said it will defy this second return to work order, after an earlier one had been ignored. The earlier one also ordered the union to submit to arbitration.

The union allowed a second return-to-work order from the Canadian government to expire on Monday, halting the airline's operations for a third day.