Originally Posted by
dieselbear
Yes. You'll have to exit and reclear*.
While the shuttle that runs between UA domestic and international actually has a stop by the US Air gates in the same terminal as AS, it goes to the UA wing of the Intl terminal. BA is in the other wing.
* Unless you have a really long layover at SFO. Some AS morning flights that originate in SEA and PDX arrive at the Intl terminal because they continue on to Mexico. But the afternoon flights all arrive at the domestic terminal.
Not to hijack the thread, but...
As I have a habit of exploring as much of any airport I transit through, I'm always interested in transiting between terminals without exiting security. At one moderately-long layover in SFO on UA, I wanted to explore the international terminal, but I wasn't sure if the UA shuttle bus people would ask me to display a boarding pass for a flight out of the international terminal.
Do they require this, or can anyone just hop on the bus and wander?