[standardUser]

There's almost a dozen other national-ish airlines and a few dozen regional and commuter airlines, but it's hard to compete with the big ones because they can't offer the same number of routes. I fly JetBlue whenever I can because I'm tall and they have the best legroom, but about half my trips end up on other airlines because JetBlue doesn't fly everywhere. But people who fly a lot and use Delta or United can travel virtually anywhere without ever having to go "out of network". The smaller airlines can capture the people who frequently take a small number of routes, but the best customers are always going to gravitate towards an airline they can use a much as possible to maximize status and rewards.