Originally Posted by jsloan

It's not automatic, but if you are booked on a P through fare to ORD (which is likely the case, since I'd be surprised if you could combine a PEK-SFO P fare with an SFO-ORD Y fare, and it'd be very expensive if you could), you should be able to waitlist for a P fare on SFO-ORD. A United agent should be able to do this, although it may take a couple of tries before you get someone who understands the situation. If your waitlist request doesn't clear, it should carry over to the gate list. Exactly where you'd be on that list, I wouldn't care to guess.