Originally Posted by jsloan

Spirit's business model is entirely different from UA's, and they're doing quite a few things that United can't do themselves, like pay their employees substantially less than UA does. Spirit's cost per available seat-mile is about half of UA's, meaning that they can actually profit on economy passengers -- but most of their profit is coming from ancillary charges. $55 -- each way -- for a carry-on paid at the airport, for example.