The prospect of a takeover of Spirit Airlines threatens to upend the cheap-fare end of the industry much like a series of mergers among big airlines reduced choices for travelers.
Spirit is the largest budget airline in the United States, but its days as a stand-alone company appear numbered. The big question is whether it is sold to fellow discounter Frontier Airlines or to JetBlue, which operates more like the four giants that dominate the U.S. airline business.
