Originally Posted by
ok2uselane
Unfortunately, UA refuses to change the codes when I tried to do this. They insist that I only "paid" for the business class (on the second segment), even though I used first class miles for the entire trip. They said that if OZ changes the equipment, I would still have to pay for the upgrade in service. Very disappointing/illogical.
No, it is not illogical and they didn't do anything wrong.
If the plane is 2 class, of course they will only book you in I class, as I class will be the highest award booking class available, and it doesn't matter your entire trip using first class miles, as long as it is 2 class, it would be I class on that segment, not O class.
What I was talking about is if the plane change to 3 class, and they sell as 3 class (if they do 3 class sell as 2 class, they will / can still only book you in I class), then you can call them up, provide there is O class inventory available using UA miles, and ask them to change from I to O. (there is no automatically rebook from I into O on *A partners)