The main terminal is where you will find the A, B, C and D Concourses and is also the entry and exit point to the airport - all trips either begin or end at the main terminal. The A and B Concourses are located in the southern half of the airport, while the C and D concourses are in the northern half, and are all connected and reachable via walking in the main terminal. The SEA Underground can be used to connect between different concourses in the main terminal, however not all concourses have direct connections, and if your gates are reasonably close, you may not save any time using the SEA Underground.

The S Concourse, also referred to as the South Satellite Concourse, is reachable via the SEA Underground from Concourse A and B (Concourse A is the quickest route from the entrance). It's a common concourse for international flights. Concourse S has limited dining options with Dungeness Bay Seafood House and Moe's Kitchen, and it also sports a Duty Free shop.

The N Concourse, also referred to as the North Satellite Concourse, is reachable via the SEA Underground from Concourse C and D (Concourse D is typically the quickest route from the entrance). It has a small number of restaurants, including Skillet, Tundra Taqueria, Bambuza and Wendys. There are also a couple of cafes located in the N Concourse.

While not technically a terminal or concourse, the newly constructed International Arrivals Facility is located on the eastern side of Concourse A. International travelers will disembark at either Concourse A or S depending on the flight; arrivals at the S Concourse will use a large elevated walkway to reach the International Arrivals Facility, which has facilities for baggage claims and customs before exiting into Concourse A.

All check-in, including tickets and baggage, happens in the main terminal on level 5. If coming to the airport by taxi, you will typically be dropped off curbside on Departure Drive on level 5, and simply need to enter the airport and find your airline of choice. If arriving by shuttle or parking your car at the airport parking garage, you will need to take the elevator or stairs to level 4 of the parking garage, at which point you will use a skybridge to cross to the main terminal, and then take an escalator up to level 5.

If you arriving after dropping off a car at the renal facility, the rental car shuttle will drop you off at either the north or south end of Arrival Drive, right outside baggage claim. Enter the main terminal at level 3, and take an elevator or escalator up to level 5. For light rail, you will enter the parking garage on level 4 and follow signs to the nearest sky bridge to cross over to the main terminal and then take an escalator to level 5 for check-in.

Seattle International Airport has 5 security checkpoints, numbered 1 through 5. Checkpoint 1 is the farthest south, or on the left most side if heading towards the security checkpoints after passing by ticketing. Each checkpoint has different operating hours and screening types available, and operating hours can change due to staff shortages or traffic volumes.

Checkpoints	Screening Types	Operating Hours
Checkpoint 1	CLEAR & TSA PreCheck Screening	4 a.m. to 1 p.m.
Checkpoint 2	CLEAR, General and Premium Screening, and SEA Spot Saver	4 a.m. to 11 p.m.
Checkpoint 3	CLEAR, General and Premium Screening, SEA Spot Saver, and SEA Visitor Pass	General: 24 hours CLEAR: 6 a.m. - 4 p.m TSA PreCheck : 10 p.m. to 4 a.m.
Checkpoint 4	CLEAR, General, and TSA PreCheck Screening	4 a.m. to 10 p.m.
Checkpoint 5	CLEAR, General and Premium Screening, and SEA Spot Saver	4 a.m. to 6 p.m.

The SEA Underground, formerly called the Satellite Transit System (STS), provides access between the various concourses in the Seattle Airport, and is the only way to access the N and S concourses. It runs underneath the airport, hence the name, and is accessed by descending stairs or escalators from the concourses. It's composed of three separate lines, the Blue Line, Green Line and Yellow line. The Blue Line connects concourses A, B and S, while the Green Line connects concourses C, D and N, and the Yellow line connects concourses A and D.

The aiport has a parking garage with capacity for 13,000 cars, which happens to be the largest single parking structure in the United States. The 4th floor of the parking garage is for Terminal Direct, which can be reserved and is a higher price than General Parking. Terminal Direct is on the same level as the sky bridges which provide access to the main concourse, meaning you do NOT need to take an elevator or stairs to reach ticketing after parking. General parking is found on all other levels, and is not reserveable. For those with an electric vehicle, in General Parking on the 7th floor of the SeaTac Airport parking garage in rows E & F are two banks of electric car chargers for a total of 34 Level 2 chargers. The spaces are reserved for electric cars, and while there is no cost to use the chargers, it is relativelty common for all non handicap spots (2) to be in use. There are numerous offsite parking options available as well.

Located across from gate A1 in between security checkpoint 2 and 3, the children's play area contains a number of small play structures in a carpeted room, and is a popular place for youngsters to enjoy themselves prior to a flight. The children's play area has a family restroom and nursing room attached to it.

Seattle Airport has numerous water bottle refill stations after passing through the security checkpoints, which mandate that water bottles must be empty. You will find the stations near restrooms in all the concourses.