**FILE** In this photo from Oct. 5, 2010, an American Airlines jet (right) taxis past United Airlines and United Express jets at O'Hare International Airport in Chicago as the Willis Tower looms in the background. (Associated Press)

Photo by: M. Spencer Green

**FILE** In this photo from Oct. 5, 2010, an American Airlines jet (right) taxis past United Airlines and United Express jets at O'Hare International Airport in Chicago as the Willis Tower looms in the background. (Associated Press)