I am currently on my UA promotion RTW ticket. I had a situation where I had to be in GUM, but Star Alliance only offered service in and out through KIX, so I booked my first leg through SPN, then I purchased my own CO o/w to GUM. My next flight leg leaves GUM through KIX. While I am returning to the same city at the end of my trip, reading the rules, you are allowed to end in any US city, so long as the city you end in isn't further East/West of the starting city, depending on your direction of travel. I started in ORD and headed west, so I could have ended my trip at JFK, for instance.

I had a difficult time finding knowledgeable help, even through the Mileage Plus line. But, if I didn't answer your question, call MP...they are the only ones with access to the promotion codes. Hope this helps.

Cheers, Marquis790