Southwest Airlines (LUV +3.8%) CEO Gary Kelly weighs in on the state of his firm in a frank...

Southwest Airlines (LUV +3.8%) CEO Gary Kelly weighs in on the state of his firm in a frank letter to employees, seeing a major challenge for LUV emerging from the transformation of legacy carriers to "better versions with lower costs. Kelly on DAL, UAL, and AMR: "...over the longer term, we're going to face a more formidable opponent, just like we now face with United, who is performing the best they have in 20 years, and also Delta, also performing very well and in some ways better than Southwest Airlines."