I just finished the phone conversation with my father, who is currently in SEA and ready to fly back to Taiwan. He flies UA SEA-SFO on F and connects to SQ SFO-HKG on C in the same ticket (issued by SQ). The final sector is CX HKG-TPE on C with a separate ticket. Here is the situation he encountered with UA SEA agent.

1. Agent told him alchohol is not allowed even in checked bag when he asked agent to put "fragile" tag on his checked bag. Supervisor told him that he can buy some sort of box, place the alchohol bottle in the box, and then he can check that box. It ended up that my father decided to give up the alchohol and gifted to UA SEA agent.

2. UA SEA F check-in agent said, his bag cannot be checked through to TPE with no reason. Two years ago, I had no problem to check my bag all the way to TPE on UA DEN-SFO connecting to CX SFO-HKG-TPE with separate ticket. I don't really know what happened here.

3. My dad told me that the F check-in agent asks him to use machine rather than manually check-in for him. I am thinking that is probably the reason he cannot check his bag all the way to TPE. Of course, he isn't issued SQ SFO-HKG boarding pass, either.

I sort of remember seeing some threads here talking about no alchohol in checked bag, but cannot find it. Any comments or thoughts which can clarify this situation would be very welcomed and appreciated.