undw - minor point, AC Jazz is not a lo-co, it's a wholly owned regional operator; uses a variety of Embraers and 'props. AC did have a lo-co called Tango that tried to respond to WestJet in the earlier nought-ies, but which was eventually rolled back into mainline. The name lived on as the cheapest/least flexible ticket designation on AC.
North America will, for a variety of reasons, never see a lo-co market like the one we have in Europe. There have been various attempts, and apart from Southwest (which has too many frills and too high a commitment to customer service to count as a lo-co in my eyes) none of them has worked. Google passenger feedback on other forums about the short lived Skybus from a year or two ago. American SLF, it seems, do not take kindly to the lo-co equation. I can't speak on their behalf, but I also suspect that North American employees in the airline industry take kindly to, for example, a FR model of business management.