Connecting at SFO: a full loop, with one long way round

Last checked 30 September 2026

At San Francisco, a hub for both Alaska and United, a project finished in 2024 connected every terminal into one loop behind security. There's one exception worth knowing about, and it's not really an exception to the security rule — just to what "behind security" actually means in practice.

At a glance

• Every terminal, 1 through 3 plus the International Terminal: connected in a loop behind security since June 2024. Whichever two terminals you're using, you shouldn't need a second security line.
• The one real catch: the International Terminal's two boarding areas, G and A, aren't directly linked. Getting from one to the other while staying behind security means walking about half the loop, through Terminals 1, 2 and 3 — reported at 15 to 25 minutes. Some travellers with PreCheck say it's quicker to leave security and re-enter instead.
• Arriving from abroad, connecting onward: you'll clear passport control and customs at the International Terminal, then recheck your bags and go through security again before your next flight. SFO doesn't have one of the small number of shortcuts around this.
• SFO's passport-control wait: a typical wait of about 14 minutes, about 41 minutes on a slow day.

One loop, one long way round

Terminal 1, Terminal 2, Terminal 3 and the International Terminal form a ring, and since mid-2024 every one of them connects to the next without leaving security. Terminal 3 is United's, both domestic and international. The other terminals' exact airline lineup isn't something this guide can confirm right now — sources disagree on which terminal Southwest uses, among other details — so check your boarding pass for Alaska, American, Delta, JetBlue, Southwest and the other airlines based here.

Here's the one thing worth knowing before you assume "behind security" means "quick": the International Terminal is actually split into two separate boarding areas, G and A, and they aren't next to each other. Getting between them without leaving security means walking about half the loop, past Terminals 1, 2 and 3 — reported at 15 to 25 minutes. If your connection involves both G and A gates, don't assume it's a short walk just because nothing stands in your way; some travellers with TSA PreCheck say it's actually quicker to leave security and clear it again at the other end.

Arriving internationally

International arrivals clear passport control and customs at the International Terminal. If you're connecting onward, you'll collect your bags, recheck them at a nearby counter, then go through security again before your next flight — the standard routine most international arrivals face at a big US hub. SFO doesn't have one of the small number of shortcuts that skip part of this.

Passport control here tends to run close to the middle of the pack for a major hub: about 14 minutes typically, about 41 minutes on a slower day.

Tips

• If your connection is between the International Terminal's two boarding areas, G and A, budget 15 to 25 minutes for the walk, or consider clearing security again if you have PreCheck.
• Otherwise, the loop makes most SFO connections a straightforward walk — just know which terminal you're headed to, since the distance depends on how far round the loop you're going.
• Landing internationally, build in time for bag claim, customs, the recheck and the second security line, on top of whatever the passport-control queue looks like that day.

Checked and reviewed 30 September 2026. Terminals and procedures change, so confirm with the airport and your airline before you travel.