Their secret sauce is their cheapness and that's what their pax look for. If I had to guess I would expect them to go for 757's, not 737's. The former have proven themselves as the workhorses of the leisure segment of the global airline industry. AA flies lots of 757's and far fewer 737's (800 series only) and that's where the ALGT's maintenance will go. B757's are the next best bargain.