Air Canada is the flag carrier and the largest airline of Canada by fleet size and passengers carried. Headquartered in the borough of Saint-Laurent in Montreal, the airline was founded in 1937 and operates a fleet of 335 aircraft serving 208 destinations worldwide through its major hubs at Montréal–Trudeau, Toronto–Pearson and Vancouver. It is a founding member of the Star Alliance. In 2025, the airline transported 45.3 million passengers.

Canada's national airline traces its origins to the Canadian federal government's 1936 creation of Trans-Canada Air Lines (TCA), which launched its first transcontinental flight routes in 1938. TCA was renamed Air Canada in 1965 and was privatized in 1988 following the deregulation of the Canadian aviation market. In 2000, Air Canada acquired its largest rival, Canadian Airlines. The carrier filed for bankruptcy protection in 2003 and emerged from restructuring the following year.

Air Canada operates a mixed fleet of Airbus and Boeing wide-body aircraft on long-haul routes alongside narrow-body aircraft on short- and medium-haul services. Its divisions include Air Canada Cargo, Air Canada Express, Air Canada Jetz, and Air Canada Rouge, while subsidiary Air Canada Vacations offers vacation packages to more than 90 destinations. Together with its regional partners, the airline operates an average of more than 1,600 scheduled flights daily.

Air Canada's predecessor, Trans-Canada Air Lines (TCA), was created by federal legislation as a subsidiary of Canadian National Railway (CNR) on 11 April 1937. The newly created Department of Transport under Minister C. D. Howe desired an airline under government control to link cities on the Atlantic coast to those on the Pacific coast. Using $5 million in Crown seed money, two Lockheed Model 10 Electras and one Boeing Stearman biplane were purchased from Canadian Airways and experienced airline executives from United Airlines and American Airlines were brought in.

Passenger flights began on 1 September 1937, with an Electra carrying two passengers and mail from Vancouver to Seattle, a $14.20 round trip, and, on 1 July 1938, TCA hired its first flight attendants. Transcontinental routes from Montreal to Vancouver began on 1 April 1939, using 12 Lockheed Model 14 Super Electras and six Lockheed Model 18 Lodestars. By January 1940, the airline had grown to about 579 employees.

Canadian Pacific Airlines (CP Air) suggested in 1942 a merger with TCA. Prime Minister William Lyon Mackenzie King rejected the proposal and introduced legislation regulating TCA as the only airline in Canada allowed to provide transcontinental flights. With the increase in air travel after World War II, CP Air was granted one coast-to-coast flight and a few international routes.

Originally headquartered in Winnipeg, also the site of its national maintenance base, the federal government moved TCA's headquarters to Montreal in 1949; the maintenance base would later also move east. With the development of the ReserVec in 1953, TCA became the first airline in the world to use a computer reservation system with remote terminals.

By 1964, TCA had grown to become Canada's national airline and, in 1964, Jean Chrétien submitted a private member's bill to change the name of the airline from Trans-Canada Airlines to Air Canada, which TCA had long used as its French-language name. This bill failed but it was later resubmitted and passed, with the name change taking effect on 1 January 1965. Elizabeth II, the Queen of Canada, flew on the first aircraft to bear the name and livery of Air Canada when she departed for the United Kingdom at the end of her 1964 tour of Prince Edward Island, Quebec, and Ontario.