Southwest has continued to grow over decades of airline bankruptcies, mergers, and pricing shenanigans. If you are a first class or business traveler, that is what the other airlines are focusing on, go with them. If you are just a regular flyer, southwest focuses on your demographic. Things they do that almost no other US carrier does. Two checked bags are free, good to cheapest fares, same price whether you buy a one-way or round trip, cancel your flight anytime and get full credit for it on your next purchase. These are great features I use all the time. I always fly them if they have non-stop flights to where I need to go.