A FlyerTalk Posting Legend
Join Date: Sep 2012
Location: SFO
Programs: AC SE MM, BA Gold, SQ Silver, Bonvoy Tit LTG, Hyatt Glob, HH Diamond
Posts: 44,331
I was always under the impression that upgrade availability was based on just that one segment.
Booking FRA-YYC-SFO deals with married segments, but upgrading it shouldn't.