Connecting at Seattle: a train to two satellites, and a streamlined arrivals process

Last checked 30 September 2026

At Seattle, a hub for both Alaska and Delta, every part of the airport sits behind one security check — but two of its six concourses can only be reached by train, and Seattle was the first large US hub to streamline its international-arrivals process, back in 2022.

At a glance

• Concourses A, B, C and D: close enough to walk between for some pairs, all behind the same security.
• The North and South Satellite concourses: no walkway to the rest of the airport at all. The only way there or back is a dedicated train, staying behind security the whole way.
• Arriving from abroad, ending your trip in Seattle: since 2022, a process lets you collect your bag once, clear customs with facial recognition, and walk straight out — no second stop for your bag, no train.
• Arriving from abroad, connecting onward: a separate checkpoint handles this, open 6 a.m. to 9:45 p.m. Outside that window, you'll need to leave security and go through one of the main checkpoints instead.
• SEA's passport-control wait runs longer than most hubs in this set of guides: a typical wait of about 18 minutes, about 54 minutes on a slow day.

One security zone, one train to the satellites

Every checkpoint at SEA connects to every gate — there's one connected zone behind security, not several separate ones. Concourses A, B, C and D are close enough that some pairs are a straightforward walk. The North and South Satellite concourses are different: there's no walkway to them at all, only a dedicated train called the SEA Underground, running on three lines every 3 minutes, that never leaves the secure area. Alaska is based mainly at Concourse C and the North Satellite; Delta is mainly in Concourses A and B.

Arriving internationally

International arrivals process through the airport's International Arrivals Facility. If Seattle is your final stop, a process introduced in 2022 — Seattle was the first large US hub to do this — lets you collect your bag once, clear customs using facial recognition instead of paperwork, and walk straight into the main terminal.

If you're connecting onward, it works differently: there's a separate TSA checkpoint just for connecting passengers, open 6 a.m. to 9:45 p.m. Outside that window, you'll need to leave security and clear one of the main checkpoints instead. The Port of Seattle's own published guidance recommends 120 to 180 minutes for this kind of connection.

Passport control here tends to run longer than most other hubs covered in this set of guides: a typical wait of about 18 minutes, and about 54 minutes on a slower day.

Tips

• Heading to the North or South Satellite, build the train into your plan — it's the only way there, not an optional shortcut.
• Connecting from an international arrival, remember the checkpoint closes at 9:45 p.m. — outside 6 a.m. to 9:45 p.m., you'll need the main checkpoints instead.
• SEA's passport-control queue runs longer than average here, so build in a bit more cushion than you might at a smaller international gateway.

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