Seattle-Tacoma International Airport has opened its new C Concourse Expansion, a $399 million, four-floor addition that adds more than 145,000 square feet of passenger space inspired by the natural landscapes of the Pacific Northwest.
The expansion, located between the C and D Concourses, replaces what was previously non-public office and storage space. It opened on 10 June 2026 as the latest project under the Port of Seattle’s Upgrade SEA programme.
At the centre of the new space is the Tree at C, a forest-inspired architectural structure that rises to a 30-foot ceiling and serves as both a gathering point and a circulation path through the building. Each floor is set back slightly to preserve open sightlines throughout the atrium, and folded facade windows with electrochromic glazing adjust automatically to filter natural light as the sun moves.
The Lookout at C offers passengers an airfield observation area, while a three-story Marketplace brings together ten new dining and retail outlets. These include local names such as Olympia Coffee, Great State Burger, Seattle Macaron Co., and Nanny’s BBQ alongside national options including Buffalo Wild Wings Go and Chili’s. Six additional retail kiosks have been launched under the SEA Sparks Incubator Program, giving emerging local artisans short-term space to trade inside the airport.
New passenger amenities include an Interfaith Prayer and Meditation Room, a Sensory Room, a Nursing Room, and a performance area. The spaces were designed to serve a wide range of traveller needs and backgrounds.
“SEA is one of the most space-constrained airports in the country while welcoming the 11th largest number of passengers. So, our teams had to get creative,” said Wendy Reiter, SEA Airport Managing Director. “We couldn’t go out, so we had to go up. Using the same footprint, and not losing any gates, we’ve created more comfort and utility for our travelers.”
The project is targeting LEED Platinum certification, which would make it the highest-rated facility at SEA. It is also the first all-electric project at the airport, with fossil fuel-free heating systems, tenant hot water, and cooking equipment throughout. Rooftop solar panels are expected to generate between 12 and 14 percent of the facility’s energy needs.
“The C Concourse Expansion represents more than a new building for the Port of Seattle — it demonstrates what is possible when innovation, environmental leadership, and partnership come together,” said Ryan Calkins, Port of Seattle Commission President. “The Port is proud to deliver a transformative space that elevates comfort and connection while advancing its climate goals.”
A public art programme runs throughout the concourse. Works include glass sculptures, digital displays, and table-embedded art pieces from artists including Crystal Worl, Fumi Amano, Jaq Chartier, Beccy Feather, and June Sekiguchi. A giant video wall at the west end of the concourse level rotates digital works from four additional artists.
Turner Construction served as construction executive on the project. “The C Concourse Expansion provides passengers with more opportunities to relax, recharge, and connect while reflecting the unique character of the Pacific Northwest,” said Kevin Stilwell, Vice President and Construction Executive at Turner Construction.
The $399 million project was funded through the Airport Development Fund and future revenue bonds. No taxpayer money was used. The expansion is part of the broader Upgrade SEA initiative, which has been delivering a series of infrastructure and passenger experience improvements across Seattle-Tacoma International Airport.
