Seattle-Tacoma International Airport has completed its C Concourse Expansion (CCE). The $399 million project almost tripled the size of the existing concourse, from 81,000 sf to 229,500 sf, and added four new floors above the building.

Designed by The Miller Hull Partnership and Woods Bagot, CCE aimed to improve the passenger experience by enhancing circulation, comfort, and accessibility in the Pacific Northwest’s busiest airport.

The facade features alternating south- and west-facing vertical glass panels, each with dynamic tinting electrochromic glass to reduce glare while increasing daylight. The interior also emphasizes natural light, with a two-story, daylight-filled marketplace. Dining and retail surround an open, tiered seating area designed for live music and informal gatherings.

“As the day progresses, the concourse responds to the changing light and weather of the Pacific Northwest,” Rich Whealan, principal at The Miller Hull Partnership, said in a statement. “On overcast, cloud-rich days, visibility is maximized to highlight the views of the airfield and Olympic Range, while soft, even daylight fills the interior, enhancing comfort and connecting travelers to the surrounding landscape.”

The Grand Stair connects the concourse to mezzanine-level amenities. In the central area, the Tree at C, a sculptural wood element, rises from the Grand Stair and branches into the wood ceiling—referencing the forests of the Pacific Northwest.

CCE’s Lookout at C is the airport’s first public outdoor space on the airside, enclosed in glass and open to all passengers for unobstructed views of the airfield and the Olympic Mountains. Amenities also include an interfaith prayer and meditation room, nursing room, sensory room, and pet relief area.

CCE represents other firsts for the airport as well, such as its first photovoltaic panel installation, first all-electric project, and first project to target LEED Platinum certification.

In addition to the 500 kW photovoltaic array, which will produce 12% of CCE’s annual energy, the project’s sustainability strategies include all-electric, fossil fuel-free systems for heating and hot water; low-flow water fixtures; waste-reduction and food-donation infrastructure; and biophilic design strategies.

Seattle-Tacoma International Airport’s $2.5 billion renovation of its S Concourse is scheduled to start in 2027.

On the project team: Port of Seattle (owner), The Miller Hull Partnership and Woods Bagot (architects), Magnusson Klemencic Associates (structural/civil engineer), PAE Engineers (mechanical/plumbing engineer and sustainability), Arup (electrical engineer), Turner Construction Company (general contractor and construction manager).