Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
As the OP will be flying domestically out of ORD, AA or UA (each of which has a hub at ORD) would be the obvious choices.
To where does he want to fly when redeeming miles, and in what class of service?