Avoiding UA baggage fees
 

I am an UA Premier Platinum but am booked on my next UA domestic flight with a Frequent Flyer number of another *A carrier on which I have no status at all.

Presume the check-in computer will automatically demand a checked bag fee from me? Can I get around that by showing my UA Premier Platinum card, while still crediting my miles to the other *A carrier?

My guess is if you show your Platinum elite card at check in that they would enter that on your record in order to get free bags and thus your trip would be credited to your MileagePlus account.

This will be check-in agent dependent, YMMV. Strictly speaking, it is one or the other. You can get UA benefits but only when you credit UA.

You can just put your MP # on the reservation, and then check in. After check in, have the agent just change the FF. This works every time for me. I use my UA*S to check in, check bags and select E+, then have an agent change my FF to my TK*G, visit the UA Club, and then go to the gate and have the GA change it. That was the way I used to do it, I have since figured out that I can just travel on my UA*S and the agents at the club can verify *G status by giving them my card. That is besides the point....

Bottom line... I my experience, you can freely change your FF at the airport up until departure.

Doesn't OP get one bag waived based on being *G on a *A flight?

1 bag x 50 lbs for non-UA *G vs UA Plat 3 bags x 70 lbs for UA domestic flight

but OP specifically stated

Ahhhh.