Spirit & Frontier (and Ryanair in Europe among others) are actually classed as ULCC's (ultra low cost), where everything is nickel and dimed. At the higher end

Spirit & Frontier (and Ryanair in Europe among others) are actually classed as ULCC's (ultra low cost), where everything is nickel and dimed. At the higher end, it certainly isn't necessarily the best any more, but I do think that's mostly because Southwest has kept to its two free checked bags, whereas the major carriers now make significant revenues from checked bag fees.