I originally signed up for the AA bonus because I thought I may use them for a trip, however, I still need to cover my trip to Poland next Summer and need UA miles more than AA, which is why I was asking about trading them.

I never travel domestically, so I would not be sad if I could not earn miles though AA, and it is not like I am doing this all of the time, this is just a one time thing.

Instead of selling miles, couldn't I just book an award with the broker and have them pay me?