Any chance ORD is so senior at AA that it might become junior shortly? I.E., is it so top heavy that it will be hit first and hardest when retirements start happening in earnest in a few years?
That does happen... Witness LAX over the last couple of years.
Whether it will or not is more difficult to predict, ie; what is the backlog of people who would rather commute to ORD than to wherever they are commuting to now?
There are however signs that it may be beginning to happen at ORD.
Bid what you want. Take the first class offered. If that is AA then by the time UAL calls you'll have a decent idea what to do.