The customer base may be there in Alberta, but the operating economics are not. The majority of the plane would be filled with Tango fare payers, so any profit would be slim at best. Planes can generate more money on routes with heavy business demand, thus paying the bills that the back cabin is no longer able to generate. WS can manage a better ROI on this route with its 737s but AC can't so doesn't bother. WS has no need to fill a front cabin, but AC relies on it to make a profit on each of its routes...even if many of those in that cabin have upgraded from the back (albeit have paid a higher price/premium to do so than the rest of the back cabin customers). A tourist/vacation route is not the place to deploy a valuable wide body that because of time zones would be out of commission on a higher yield route longer. (While CUN is a tourist/vacation route, the aircraft can fly down overnight and return early enough in the day to be put onto another route each week after it gets back. Time zones are not as problematic down there as they are to/from Hawaii.)