Originally Posted by Kacee

Yes it's clear from the schedule that UA is assigning Polarized 772s to specific PE routes, including SFO-HKG, SFO-LHR, and SFO-FRA. They have enough of them now that it's a fairly large subfleet. By concentrating these aircraft at specific hubs (particularly SFO and EWR) they minimize the risk of not having a properly configured aircraft. This is why you're seeing 787s finally being assigned to ORD . . . they've swapped them for the now Polarized 772s.