Current Initiatives

Relieving Congestion: Concourse D Annex

A new annex uses space more efficiently and accommodates our growing number of passengers.

Designed to relieve current congestion, our Concourse D Annex project saves passengers time waiting for a plane to arrive at a gate, helps reduce greenhouse gas emissions from idling aircraft waiting for an open gate, and saves airline fuel.

The new 32,400-square-foot space provides SEA with six holdroom gates and allows for what is called ‘hardstand operations.’ This means passengers are shuttled to and from an aircraft parked away from the terminal building.

Moving more people with less congestion

Accessing the facility

Travelers access the facility from Concourse D, over a bridge to a two-story terminal. The sky-lighted curved roof structure is designed to be 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 that takes them to the aircraft parked away from the terminal.

Arriving passengers deplane at a hardstand location, board a shuttle and 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.

Congestion Relief

SEA continues to be one of the fastest-growing large hub airport in the U.S., with passenger traffic increasing 43 percent. In the last five years, annual passenger traffic has grown from 33.2 million in 2012 to 49.8 million passengers in 2018.

With this growth, all of SEA’s contact gates are in use during peak periods of operation – that is, where an aircraft is connected by a passenger loading bridge to the terminal.

Building Sustainably

Energy-saving features and sustainability measures are designed into the annex. These include water-efficient fixtures in the restrooms and energy-efficient radiant floor heating. Landscaping outside the facility is irrigated by water coming off the roof.



Sep 2017
Oct 2018
Concourse D Annex open


The total cost to build the $38.4 million facility is financed with short-term revenue bonds and debt service will be included in airline rates and charges.

Project Fact One
Passengers are shuttled from their gate to the aircraft parked away from the terminal.
Project Fact Two
The Port is currently pursuing LEED certification for the Concourse D Annex.
Project Fact Three
Sustainable features include a rainwater management system, radiant floor heating, natural light and locally sourced materials.
Project Fact Four
95 percent of the construction waste from the project was recycled.
Checking in on the new Concourse D Annex facility at SEA