About 1 1/2 years ago an airside connection was opened connecting the International terminal to T3/North UA terminal. No need to exit
http://www.flyertalk.com/forum/unite...kway-open.html
from the
SFO site
Transferring from Terminal 3 to the International Terminal
Passengers on flights arriving at Terminal 3 may transfer to International Terminal Boarding Area G via a connector walkway linking the two terminals. The entrance to the connector is located post-security in Terminal 3 near Gate 75, and the exit is located post-security in International Terminal Boarding Area G near Gate G92.
There are two sections of the international terminal, UA flights are in the G section. You can get to the A section either also airside but it is a long walk -- hence the suggestion to use the airtran