Well, I asked about this in HKG. It was a ticket issued by a US travel agent, on CX stock, but with an AA segment. The staff at the lounge in HKG couldn't figure out how to do it or if it was even doable, they tried contacting their US ticket office but I think because of the time change nobody was there and so they couldn't do anything, and they had about 2 hours to do so. Pretty poor service, and a potential missed revenue opportunity I guess.