United Airlines, the busiest carrier at O'Hare and the hometown carrier, opened its futuristic terminal in 1989. United operates from a landside and midfield concourse. O'Hare is the world's second busiest airline hub and airport. United has an edge in marketshare over American. These airlines each have their own terminal while the other 2 terminals accomodate everyone else and international flights. ORD began operations in 1962 when Midway became too small for the jet age. As most know, MDW was resurgent in the 1980s with the arrival of Midway Airlines, Southwest, and ATA.