Originally Posted by
paperwastage
why not?
you log onto your 480-Plus-Points UA account and use those points to upgrade someone else (yourown ticket accrualing to another FF) ?
It's too risky as if you log in to your booking when your MileagePlus account is open ( logged in ), during booking the flight, viewing it via manage my booking, or checking-in on a web browser or the app; the system would auto-assign the MileagePlus number to the traveler matching the name of the traveler.
If you want to use them and credit miles to another FFP, you need to be super-cautious when using the UA website.