On Sunday morning I will arrive at SFO terminal 1 on a US Air flight. I connect with United for a flight overseas in the international terminal G. I have a tight connection and need to know the fastest way to get from terminal one to Terminal G.

I have read that United has a bus (by gate 38) from terminal one to terminal G but I am not sure if that will be available as I am arriving on US Air. If this bus will be available, will I have to exit and enter security when going from terminal 1 to G on the shuttle bus?