The best price found from United States to Canada is on October 4th, 2016, travelling with Porter Airlines. See more options, compare prices and book: search flights.
Toronto is far and away the busiest airport, followed by Vancouver. The international gateways you're most likely to use:
Air Canada, the national flagship carrier, is considered one of the world's safest airlines. All major global airlines fly to Canada. Other companies based in the country and serving international destinations:
WestJet (www.westjet.com) Calgary-based low-cost carrier serving destinations throughout Canada, flying to Varadero, Cayo Coco, Santa Clara and Holguín.
Porter Airlines (www.flyporter.com) Flies in eastern Canada and to US cities, including Boston, Chicago, Washington, DC, and New York.
Air Transat (www.airtransat.com) Charter airline from major Canadian cities to holiday destinations (ie southern USA and Caribbean in winter, Europe in summer).