How does Southwest Airlines keep making money? After all, t he airline industry overall is in a shambles. US Airways and United Air Lines are reorganizing in bankruptcy while American Airlines flirts with the same fate. As a group, the nation’s biggest air carriers have lost billions of dollars over the past several years, with no immediate recovery in sight. The secret to its success, said Southwest chairman Herb Kelleher during a talk at Wharton April 22, is available for anyone, including its competitors, to see. It’s an obsession with keeping costs low and treating employees well and a commitment to managing the company during booms with an eye to the busts that will inevitably follow. Do that, Kelleher said, and most of the rest takes care of itself. “To be successful in business, you need a sense of historicity and futurity,” he said. “What does that mean? Hell if I know, but it sounds good. Seriously, what I’m saying is, be prepared because the bad times are going to come.…