"We are in a situation where literally hundreds of thousands of Canadians and visitors to our country are being disrupted by this action," Prime Minister Mark Carney said.

A labor relations board declared a strike by Air Canada’s 10,000 flight attendants illegal on Monday and ordered their union to tell them to return to work by midday.

The Canadian Union of Public Employees said it will challenge an order by the Canada Industrial Relations Board to return to work by 2 p.m. ET.