A new pricing regime was the wind lifting Southwest Airlines (LUV 5.53%) stock on Tuesday. On the news that the company is falling in line with a current standard in the airline industry, investors lapped up its shares, to the point where they closed the trading day more than 5% higher in price. That compared most favorably to the benchmark S&P 500's (^GSPC 2.05%) barely over 2% gain.Bags full of new revenueSouthwest announced Tuesday it will start levying on its passengers a $35 fee for one checked bag, an ...