<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by mindgame:
CO miles to UA and/or vice versa via Amtrak Guest Rewards</font>
You can do CO --> Amtrak --> UA (and yes, it's 1:1:1), but not the other way around. You can also transfer Midwest Express miles to CO or UA through Amtrak, also 1:1:1.