I used my SO's miles to book a couple of tickets for her in-law and a niece to come visit us (PEK to SFO).

Due to the late booking, I could only find saver economy with long layover in Japan. With the current itinerary, they fly out on ANA to Tokyo, then catch United to SFO.

I just looked at the flight times, and it seems that the PEK-SFO direct flight leaves 2 hours ahead of their ANA flight to Tokyo. So I was thinking that they could just go to the airport early and see if they could catch the direct flight rather than flying through Tokyo.

Question is, even though they're on a UA award ticket, with first segment being booked on ANA metal, can they just show up at PEK a few hours early at the United counter and try to SDC to the PEK-SFO direct? (will pay the $75 SDC fee)

United doesn't seem to release X at T-3 anymore, so I'm not sure if this is possible or not. Does anyone have recent experience with SDC based on X-fare?