Air Canada and the union representing 10,000 flight attendants resumed talks late Monday for the first time since the strike began over the weekend. The strike is affecting about 130,000 travelers a day at the peak of the summer travel season.

The union representing Air Canada flight attendants vowed to fight a federal order to end their strike, calling it "blatantly unconstitutional" and accusing the government of siding with the airline.

Striking Air Canada flight attendants vowed Monday to defy another back-to-work order from Canada's labor tribunal, extending a work stoppage that has cancelled travel for half a million people worldwide.