Air Canada has delayed restarting flights until Monday evening after the union representing 10,000 flight attendants vowed to defy a government-backed back-to-work order.

CUPE invited Air Canada back to the table to "negotiate a fair deal," calling the order to end its strike unconstitutional. The airline said it would delay plans to restart operations from Sunday until Monday evening and described the union as illegally defying the labor board.

A Canadian government panel ordered the flight attendants back to work, but they refused. The strike is affecting about 130,000 travelers around the world each day.