Connecting at SFO: When You Can Stay Inside Security
Use two SFO connection examples to distinguish post-security walking from arrivals that require customs, baggage handling and fresh screening.
Maya and Leo are both changing planes at San Francisco International Airport (SFO) on the same afternoon. Their next gates are in different terminals. One of them can walk there without leaving the secure area. The other has to collect a bag, leave and go through security again. The terminals are the same; what differs is how each of them arrived.
Maya and Leo are fictional, and so are their flights. The airport details come from SFO’s own website.
“Inside security” here means the area after the security checkpoint, where the gates are. “Leaving security” means going back out to the public side and being screened again to return.
Maya: domestic arrival, international departure
Maya lands on a domestic flight and is flying on to an international destination. She already has her onward boarding pass, has no bag to collect and has confirmed that she does not need a ticket-counter visit or other stop outside security.
SFO’s connection guidance says post-security connectors are available between all of its terminals. It says passengers arriving on a domestic flight can walk to their next gate without exiting and re-entering security.
So Maya’s next step is simple: check her current departure gate and follow the connecting-gate signs. A different terminal name on her boarding pass doesn’t mean she has to leave.
Her plan assumes she can go straight to the gate. SFO directs passengers who are not checked in for their onward flight to their airline’s ticket counter; its page notes an Air Canada exception to the International Terminal Main Hall location. If you still need check-in or document help, confirm where to go with your airline before following Maya’s example. Already being checked in does not settle every airline requirement.
Leo: international arrival, domestic departure
Leo lands on an international flight that was not precleared for US entry and is connecting to a domestic flight. His checked bag is tagged to his final destination.
For passengers like Leo, SFO lists these steps:
- Complete US Customs and Border Protection (CBP) entry procedures in the Federal Inspection Area.
- Claim checked baggage after immigration and go through customs. For the non-precleared arrivals covered by this section, a bag tagged to the final destination still has to be collected.
- Exit through the doors marked “Connecting Flights.” SFO says bags tagged to their final destination can be rechecked at the baggage desks just outside. If no agent is available, or a bag isn’t tagged through, passengers should go to their airline’s ticket counter.
- Go through a security checkpoint to reach the next flight.
SFO adds that after exiting the International Terminal arrivals hall, passengers can change terminals on foot or by AirTrain. After clearing security, they can walk to any gate.
So even though Leo’s next gate is reachable inside security, he has to leave and come back in. Connected terminals don’t let him skip entry formalities, collecting his bag or a fresh security screening. This guide can’t tell Leo how long that takes or whether his connection is long enough; his airline and the booking are the place to check that.
The exception: precleared flights
Some international flights are precleared. SFO says passengers on precleared international flights don’t go through the federal inspection process on arrival. They disembark into the post-security area and can walk to their next gate.
Confirm with your airline whether your particular flight is precleared rather than relying on a country label. If Leo arrived post-security on a precleared flight and had no reason to go outside security, he could follow the connecting-gate signs like Maya.
At a glance
| Arrival | Next steps |
|---|---|
| Domestic | Walk post-security if ready for the onward flight and no outside-security stop is needed. |
| International, not precleared | CBP, collect checked bags, exit, recheck as applicable, then security. |
| International, precleared | Arrive post-security; walk onward if no outside-security stop is needed. |
Terminal 3 construction (as of November 2026)
SFO’s Terminal 3 West modernization project is underway. Its construction advisory, checked November 6, 2026, says interim post-security walkways let passengers walk between all terminals and boarding areas around the construction site. One runs from near Gate E2 in Terminal 3 to the rotunda food court and F gates area. A second runs from there to an existing post-security walkway to the International Terminal G gates.
The advisory also says the separate Terminal 3 AirTrain station is closed and directs passengers to the combined “Terminals 2 & 3” station. Construction routes can change, so check SFO’s current Terminal 3 advisory on your travel day and follow the signs in the terminal.
On the day
- Check your boarding pass and current gate before you land, and again after.
- Work out your arrival process: domestic, precleared international or not precleared international.
- Decide whether anything takes you outside security, such as checking in, collecting a bag or visiting a ticket counter.
- Follow current airport signs and alerts, not an old map or a past trip.
- Ask airline or airport staff if what you see doesn’t match what you expected.
For SFO’s own description of connections, see its international connections page.
This guide describes SFO’s published connection processes as of November 2026. It doesn’t guarantee any connection time, gate or entry outcome.