Not to hijack the thread, but my question ALMOST got answered above and maybe I could squeeze out a bit more info...
My son and I are going to FL, PHF-ATL-MLB, but in the middle of the return, he goes home and I stop in ATL for business for a couple of days.
My ticket was purchased by the company, his by me. My first instinct is to just see what happens with the UG, since it would be more fun for him to sit up front in my UG seat than for us to sit together (teenager

), should I get one. But with this situation, two different itineraries, can I set up a companion linkage, say, on the outbound leg where we are together?
(added) we are sitting together as of now, but if we get split, no big deal. But both of us front might happen on these flights, even at the bottom- and this would be the top choice.