The flights to DEN based solely on timing. At least it was a CR-700 and got 3B. The mainline times just didn't work. The IAH flight was not my first choice. Finished work 4 days early and this was all I could get. Was supposed to go through ORD and already upgraded on DTW-ORD and ORD-SFO. But those flights packed and no room. Only flight I could get changing 12 hours before leaving was DTW-IAH-SFO.