The Air Train is a bit quicker, but you can walk. The entire airport is in a circle and you can walk to all terminals. 🙂 It's probably a 15 to 20 minute walk between terminal 3 to terminal 1.
Walking would be the best option. Though there is Air Train
Agree, walking is the best option, probably faster than having to wait for the tram. SFO is surprisingly walkable, we spent four hours strolling around the airport waiting for a relative's delayed flight to arrive. Seeing cops on bikes indoors takes a little getting used to. 😆
There is a tunnel from 1 to 2
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