Under Kelleher's leadership, Southwest succeeded by a strategy of offering low fares to its passengers, eliminating unnecessary services, using a single aircraft type (the Boeing 737) (except for use of the Boeing 727 and use of MD-80 by TranStar and 717 by AirTran), avoiding the hub-and-spoke scheduling system used by other airlines in favor of building point-to-point traffic, and focusing on secondary airports such as Chicago-Midway (instead of Chicago-O'Hare), Dallas Love Field (instead of DFW), and Orange County, California but later some hub flights were operated at airports, such as ATL, LAS, PHX, DEN, STL, and BWI and some major airports, like ORD, LGA, LAX, SFO, and DEN.