Air Canada says it has suspended plans to resume limited operations after the union representing the airline's flight attendants said Sunday it will defy a federal back-to-work order for binding arbitration to end the work stoppage.

Air Canada flight attendants said on Sunday they will remain on strike and challenge a return-to-work order they called unconstitutional, defying a government decision to force them back to their duties by 2 p.

Air Canada cancelled hundreds of additional flights on Sunday after the union representing its flight attendants announced the workers would remain on strike in defiance of a back-to-work order. The Canadian Union of Public Employees said it filed a challenge in Federal Court on Sunday to an order by the Canada Industrial Relations Board that said its members must return to work by 2 p.