Sea-Tac Airport Readies Next Major Renovation: S Concourse

The Port of Seattle Commission last week authorized $1.1 billion in initial funding for the next significant modernization project at Seattle-Tacoma International Airport: renovating the 53-year-old S Concourse.

Major construction is scheduled to start in 2027.

The so-called S Concourse Evolution will cost an estimated $2.5 billion and transform the 1973 facility into a world-class concourse that primarily serves international travelers, according to a news release from the Port of Seattle, which operates the airport. The project matches recent SEA modernization project standards, including the C Concourse renovation that opened in June, ensuring increasing traveler demands are met with more space, amenities, and sustainability, including reduced energy use and greenhouse-gas emissions. There will be an anticipated 58% reduction of annual operational greenhouse-gas emissions and a 16% reduction of annual energy use.

Last week’s commission authorization is for $1.1 billion to fund the project into 2029. Commissioners will review remaining costs at a later date. Project funding comes from a combination of Airport Development Fund and future revenue bonds. No taxpayer dollars will be used, the release said.

The S Concourse work is part of the $5.5 billion Upgrade SEA capital-improvement program and will be completed in phases over eight years to allow continuous flight operations at most gates during construction and minimize traveler and airline operational impacts, the release said. A temporary S Annex east of the facility will be built to support ground boarding operations and make up for gate closures, with a goal to have three of 12 gates impacted by construction at any time. As each project phase is completed, more space will reopen to the public, with all phases estimated to be concluded by 2034.

A flythrough video shows concepts, at 60% design, for the S concourse.

Port of Seattle Commission President Ryan Calkins said the commission’s authorization for the S Concourse project “builds on the generational investments we are making at SEA to improve the passenger experience” and will add critical seismic, structural, and building systems upgrades to improve passenger circulation and operational efficiency.

The project does not add gates because there’s no room to expand between the main terminal and airfield. Instead, it repurposes, in part, the customs area vacated when the International Arrivals Facility opened in 2022. The modernization will add 150,000 square feet, including a new upper concourse level; improved dual-level boarding operations for select gates; and expanded dining, retail, lounge, and passenger amenities.

SEA Airport Managing Director Wendy Reiter called the project a necessary upgrade to improve service for travelers and tenants.

“As we’ve done in previous Upgrade SEA projects, we’re being innovative by building up and not out,” Reiter said in a statement. “We’re mindful of the fact that we have one of the smallest footprints of any major U.S. airport considering our passenger volume.”

Kevin Keady, AECOM West region business leader of buildings and places, said the design is inspired by local, indigenous concepts combined with pragmatic enhancements that will achieve greatly improved passenger service levels and meet the high standards travelers are accustomed to at one of the world’s busiest airports.

Upgrade SEA projects completed and in progress include N Concourse modernization, completed in 2021; International Arrivals Facility, completed in 2022; restroom renovations, completed in 2025; SEA Gateway Project, completed this year; C Concourse expansion, completed this year; roadway improvements, nearing completion this fall; baggage optimization, completed by 2029; and SEA underground controls replacement, completed by 2027, according to the release.