Chicago is United Airlines' mother hub. United is Chicago's hometown airline. Begining tomorrow, United will be offering flights hourly to SEA, SFO, LAX, DEN, MSP, BOS, EWR, LGA, DCA, IAD, PHL, ATL and DFW.
United offers service into and out of Chicago on the most widebodies of any other carrier in the Chicago market. Out of Chicago, there are 747s, 777s, and a lot of 767 operations. There are also tons of Airbusses, and 737s along with quite a few 757s. United's entire fleet passes through ORD at sometime or another.
While American may have more international flights out of ORD, United is very strong using it as a world hub, connecting all of the continents and star alliance hubs. Domestically, Chicago sees a very large United mainline presence.
I L U V 7 6 7