I've got an NC seat confirmed from SFO-NRT on 837 on the 19th (confirmed at time of booking a few months ago), but I've been waitlisted all along for the NC upgrade for my NRT-SIN segment on UA 801, evening of the 20th.

Although there is no upgrade/award inventory currently visible, ual.com is showing me C9 D9 for that segment, if I search for a complete SFO-SIN itinerary. It shows me C0 D0 if I search for NRT-SIN alone.

I called UA to enquire about my upgrade status/chances (since I can't get that info from "My Itineraries" online anymore) and I was told that every seat on that segment had been sold and there would be no chance of an upgrade, even though I'm at the top of the waitlist.

I guess what I'm really wondering is whether my upgrade will process against that sector alone, or across the whole flight. If one of the seats which is showing available for SFO-NRT-SIN moves into upgrade inventory, will someone else who is waiting for NC on the full route get the upgrade ahead of me, because my waitlist is only looking at inventory for the NRT-SIN portion ?

I can clearly purchase an SFO-SIN ticket online which uses 801 on the 20th, but I can't purchase that NRT-SIN segment. Which leads me to worry that the same may apply to my upgrade, depending on how intelligent the system is.