Originally Posted by
WineCountryUA
this would have been true even if two separate flight numbers -- only one "fee".
The downside is you could not waitlist just for SFO-NRT leg and if NRT-TPE only cleared, miles and co-pay still would have been charged (but usually just the reduced level).
That doesn't jive with what the UA agent I spoke with said prior to adjusting my flight schedule. I was originally on different flight numbers TPE-NRT and NRT-SFO, and the upgrade only applied to NRT-SFO and when I asked if I could apply it to the TPE-NRT leg as well, she told me that was a separate upgrade.
But I'll defer to the more experienced traveler on this one, because that was my one and only experience attempting to do this.