If you've ever flown to or from Canada, there's a good chance you've flown on Air Canada. They're the largest Canadian airline and serve many destinations around the world.
Air Canada is the national airline of Canada - They operate flights to all corners of Canada and are your best bet for getting to some of the more rmeote destinations.
Flying with Air Canada can be hit and miss - because they are the main airilne in Canada many Canadians complain about their service, and I've had both good and bad experiences with them. They are however starting to modernize more of their aircraft with tv screens in seat-backs and other such amenities. The new Air Canada Jazz airline is a good alternative with flight costs as low or even lower than WestJet.
Air Canada Vacations is another division that provides flights and hotel / resort accommodation to places like Mexico and the Carribean.
All in all, Air Canada whether you love them or hate them can't be beat for connecting Canadian cities to international and domestic flight destinations.