Air Canada cancelled hundreds of flights Saturday as it began shutting down operations in response to a strike by flight attendants -- triggering summer travel chaos for its 130,000 daily passengers.

Canada's largest airline, which flies directly to 180 cities worldwide, urged customers not to go to the airport if they have a ticket for Air Canada or its lower-cost subsidiary Air Canada Rouge.

It said flights by Air Canada Express, which are operated by a third party, would not be impacted by the walkout.

"Air Canada deeply regrets the effect the strike is having on customers," the company said in a statement.

The Canadian Union of Public Employees (CUPE), which represents Air Canada's 10,000 flight attendants, said that strike action officially began at 12:58 am local time (0458 GMT)

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