"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.

The presidents of two major Quebec unions fear workers in the province could soon face the same treatment as striking Air Canada flight attendants under a provincial law passed in May.

“This is going to be a test case for unions fighting against Section 107,” said Stephanie Ross, an associate professor of labour studies at McMaster University.