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.

Air Canada’s flight attendants stayed on strike even after the country’s labor board ordered them back to work, causing the airline to delay plans to restart flights.

Union leaders for Air Canada’s flight attendants face fines and criminal charges after defying a second order from Canada’s federal labor board to end their “unlawful” strike.