Southwest pulled it off with fuel hedges. Those don't last forever.
And yes, WN has stated that they are exploring additional fees for luggage. Don't worry, it's coming.
Don't buy that.
SWA has been touting their bags fly free in their ads at every airport I've been to in the past 5 months, plus their ads in the media. It's something they've had in their 30+ year business model, and Gary, Herb, and Co. have no intention of changing that anytime soon.
Keep in mind that there was an airline that tried to do exactly what NKS has done, and a bit worse: SKB (Skybus). Their business model: $10 fares (excluding tax), and charge for everything else at the gate. Bags? Charged. One carry-on allowed. Any others? Charged. No check through luggage, no routing to destinations. You flew to CMH, and if you were on your way to Florida, they wouldn't route your bags to that flight, nor hold that connecting flight for you. If you bought food from them, or prior to flying, you had to eat and dispose of it prior to boarding the plane.
With the bags.. sound familiar?
SKB folded in 11 months.
Also, note how other airlines who are nickel'n'diming for bags (UAL, COA, DAL, FFT, AAL, etc.) are all in a world of hurt. FFT just went Ch. 11 and was bought out by RPA! MEP was the same. SWA is doing this with much more than hedging. If it came to it, from the profits they had from the early 2000s due to their fuel hedges, they could eat the cost of the bags, whereas everyone else has been struggling to find extra revenue. In short, poor planning by the execs of the other carriers leads to their customers being nickel and dimed.
SWA has a firm head on their shoulders, and knows what their customers want. And they are giving it to them as the see it. I don't think you'll find any one flying with them today asking to be charged for checking their bags.
BL.