More than 10,000 flight attendants walked off the job early Saturday morning, leading to hundreds of flights being grounded.

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.

The union representing more than 10,000 flight attendants says the workers plan to remain on strike even after the Canada Industrial Relations Board ordered both parties back to work by 2 p.m. ET toda...