Try Interjet They fly out of Canada Toronto, Montreal, Vancouver. USA Dallas, Houston, L.A, Las Vegas, Miami, Orlando,Chicago, San Antonio, New York. Out of Canada they are by far the cheapest. They also offer extra leg room, food and liquor at no extra cost. The basic fare is for carryon only, or it cost $34Can for each checked baggage. They also have upgrades fares available. CCC friend tried them, had a very good experience with them. I will try them for our trip in end of April.
