The Canadian Union of Public Employee said the 10,000 Air Canada attendants it represents would remain on strike, calling the order unconstitutional and “designed to protect the airline’s profit.”

Air Canada has suspended plans to restart operations Sunday, after flight attendants refused to comply with a federal return-to-work order.

The federal government ordered the airline and its flight attendants back to work Saturday, ending a strike and lockout after less than 12 hours.