Originally Posted by channa

I don't know about that. UA's hubs are in much more competitive environments than CO's, so CO can afford to get away with more than UA. CO has a stronghold on EWR, IAH, and CLE while UA has direct hub competition at LAX (AA/DL), DEN (F9) and ORD (AA).

As a result, UA has to be more sensitive to its Elite travellers, as they can more easily lose them. If you live in IAH, you're pretty much stuck on CO, no matter what they do to you (hence the 50% EQM rule on CO).