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Concourse D Annex

Status: Completed in Q4 2018

Project Overview

The Port of Seattle’s Concourse D Annex project is designed to relieve current congestion for travelers waiting at crowded gates and aircraft waiting on the airfield for an open gate to deplane passengers during peak periods. The new annex uses space at SEA Airport more efficiently to provide for passengers waiting for flights, reduces the length of time passengers spend waiting for a plane to arrive at a gate, saves greenhouse gas emissions from idling aircraft, and saves airlines fuel.

This project accommodates the current passenger volumes at SEA Airport with space for six holdroom gates. The 32,400-square-foot building allows for ‘hardstand operations’ where passengers are shuttled to and from an aircraft parked away from the terminal building.

Travelers access the facility from the D Concourse, over a bridge to a two-story terminal. A sky-lighted curved roof structure makes it light and airy and includes a gently sloped ramp to the ground level and the departing gates. Amenities for passengers include concessions, electric charging stations, free airport WiFi, and restrooms. Passengers walk through a gate door to a waiting shuttle which takes them to the aircraft parked away from the terminal.

Arriving passengers deplane at a hardstand location, board a shuttle, ride to the new facility to a drop-off area at the south end connecting directly into the terminal to access the bag claim level or to a connecting flight on the secure side.

Link to YouTube video "Checking in at D Annex
Checking in with SEA Airport Managing Director Lance Lyttle on the new D Concourse Annex passenger facility. Click the image to view a short video.

Congestion Relief

SEABusy terminal at Sea-Tac Airport, Seattle, WA was the fastest-growing large hub airport in the U.S. the five years prior to the pandemic, with passenger traffic increasing about 43 percent. Annual passenger traffic went from around 33.2 million in 2012 to 46.9 million in 2017.

With that growth during peak periods of operation, all of SEA’s contact gates are in use – that is, where an aircraft is connected by a passenger loading bridge to the terminal. Just in May and June of 2018, an average of 645 flights per month were held waiting for a gate, affecting over 92,000 passengers. Aircrafts are held an average of 185 hours, using over 100,000 gallons of jet fuel unnecessarily each month. The fuel usage by idling aircraft produces 11,700 metric tons of greenhouse gases annually


The Concourse D Annex project began construction in September 2017 and opened October 31, 2018.

Estimated Project Costs

Total project cost is $38.4 million.

The total cost to build the facility is financed with short-term revenue bonds and debt service will be included in airline rates and charges.

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