Don't think I've ever tried this before. I have round-trip itinerary BKK-SFO. There's one UA segment, NRT-SFO. The return (in February) is NH operated (ticketed as UA codeshares). Will I be able to SDC the single UA segment NRT-SFO with two NH segments still on the ticket, albeit nearly two months in the future? My guess is "no" since UA would have to reissue the ticket, which will still contain partner flights, in connection with the change. But curious if others have experience with this scenario.