CHICAGO, IL - SEPTEMBER 19: A United Airlines jet taxis at O'Hare International Airport on September 19, 2014 in Chicago, Illinois. In 2013, 67 million passengers passed through O'Hare, another 20 million passed through Chicago's Midway Airport, and the two airports combined moved more than 1.4 million tons of air cargo. (Photo by Scott Olson/Getty Images)
