For decades, supersonic passenger travel has occupied an odd place between aviation history and science fiction. Concorde proved that an airliner could cross the Atlantic in less than four hours, but the aircraft disappeared from commercial service in 2003 after years of high operating costs, expensive fares, and a limited market. Now, a combination of new aircraft development, successful supersonic test flights, and changing U.S. regulations has made the possibility of high-speed commercial travel harder to dismiss. For business travelers, the biggest potential change is straightforward: journeys that consume most of a day could eventually consume only a few hours.