Discount flyer Southwest Airlines (LUV) said Friday its November traffic fell. The airline applied for slot exemptions that would allow it to offer nonstop services between Washington, D.C., and Houston. Southwest's traffic, or revenue passenger miles flown, fell 1.5% to 8.1 billion revenue passenger miles in November vs. 8.3 billion in November 2011. The results include traffic for AirTran, the flyer it finished acquiring in May 2011. Available