Warren Buffett hates airline stocks. He bought a preferred stock issue from U.S. Air in 1989. By 1995, the company had lost $3 billion, and Buffett's preferred dividend was suspended. Since then, he has been very vocal about his feelings toward the aviation industry.
The net wealth creation in airlines since Orville Wright has been next to zero. If a capitalist had been at Kitty Hawk and shot him down, he would have done us a huge favor... The worst sort of business is one that grows rapidly, requires significant capital to engender growth, and then earns little or no money. Think airlines.
But... knowing the airline industry has always been a loser for investors makes airline stocks very easy (and safe) to sell short. In fact, right now, you can easily find a half-dozen airlines that cannot afford the interest on their debts, suffer from plummeting revenues, and face huge losses related to commodity hedging.