Southwest is not really a "budget" carrier anymore. They may have started out that way in the 70s when the level of service on traditional mainline carriers wa

Southwest is not really a "budget" carrier anymore. They may have started out that way in the 70s when the level of service on traditional mainline carriers was much higher than it is now, but since then, most other carriers have adopted elements of Southwest's business model. Some of the mainline carriers have even gone further (see no free bags, charging for assigned seats, etc). Especially now that Southwest flies to major airports (DFW, BOS, ATL, the NYC area airports, SFO, etc), I would classify them pretty much the same as the rest of the majors. The only thing they don't do that the majors do is allow their fares to appear on aggregator sites. That, and the free-for-all seating (which I can't stand, but that's a different complaint). In fact, unless you book far in advance or catch a fare sale, Southwest is amazingly expensive to fly on. A couple of months ago I had to travel on short notice (death in the family, only 3 days until the funeral). An airfare on Southwest from Nashville to Boston was a 56% above the competing mainline carriers. And if I flew into Providence, which would have been more convenient, it was an astounding ~75% higher than Delta or US Airways.