Join Date: Aug 2002
Location: WAS/TYO
Programs: UA 1K, AA EXP (3MM), DL PM, BONVOY TITANIUM, HYATT GLOBALIST, HILTON DIAMOND, IHG DIAMOND AMB, et al
Posts: 6,248
Data point: just purchased a PremiumPlus ticket (R) for later this year with the connecting domestic segment booked in B. The domestic segment had PN available but no PZ (longhaul segment had PZ and was upgraded using PP), but UA.com/app was not showing the instant upgrade available to confirm. 1K Desk supervisor was able to force the instant upgrade into PN. Seems to be case of YMMV with respect to Premier Instant Upgrades for B segments on PremiumPlus fares.
-FlyerBeek