Originally Posted by
deniah
if one has MP and OP miles can they be combined into a single account without fees/reduction through ratio?
No.
CO and UA are not merging. You will
not be able to combine your MP and OP miles.
CO is simply joining the Star Alliance. That will enable you to earn MP miles on various CO flights. And, you will earn OP miles on various UA (and other Star Alliance carrier) flights.
It will be pretty much the same situation as when US joined Star Alliance.