Originally Posted by
masonuc
Is that possible... I assume yes but want to confirm. I am CP on US and Premier on UA, hoping to do this regularly this year since I prefer to keep my US status but will be flying UA a lot. Presumably I would just book the ticket in my UA account, get boarding pass and change the FF# to my US number on day of departure (once I had my boarding pass in hand).
That works but watch out for your return, as if they apply the US # to the entire itinerary then you'd get kicked out of E+ seats for that flight