I frequently get irked when people call US airlines Low Cost Carriers - LCCs. Such an animal is a rarity in the US market. The only carrier who fulfilled the model was Skybus. Westjet (sort of!).
But let's be clear. Southwest has not been one for many years. Air Tran is not. US Airways definitely is not (despite its stock symbol). Frontier is not. JetBlue is not.
So anyone who says that the US LCC market is approaching 30% (yes that means the Spin Doctors at Delwest) is smoking something.