Most airport expansions eat apron. This one went up.
The Port of Seattle finished a $399 million expansion of Concourse C at Seattle-Tacoma International Airport by stacking four new floors directly on top of a single-level concourse that never stopped operating. Flights kept pushing back underneath the work. The building grew from 81,000 sq ft to 226,530 sq ft, nearly tripling in size, and added no new footprint at a field where apron space is the scarcest commodity there is.
Project Scope
Turner Construction Company delivered the job under Washington’s GC/CM progressive construction-manager-at-risk statute, with The Miller Hull Partnership leading design alongside Woods Bagot and Jacobs handling construction management. A demising wall went up in January 2024 to separate live gate operations from the work zone, followed by what the Port called a ground bowl-breaking that March. The structure topped out in December 2024.
The added floors carry 13 new dining and retail concepts, an interfaith prayer and meditation room, a nursing suite, and an Alaska Airlines lounge north of 20,000 sq ft. The centerpiece is a timber-clad structural tree rising over a tiered amphitheater with a live-music stage, drawn from the covered public markets of the Pacific Northwest. A fully glazed observation deck called Lookout at C faces the airfield and the Olympics beyond it.
Building systems are fossil-fuel free across heating, tenant hot water and cooking. A rooftop photovoltaic array, electrochromic glazing and low-flow fixtures round out a package the Port ran through its Sustainable Evaluation Framework, the first project delivered under that process.
Why It Matters
Vertical expansion over an operating concourse is one of the harder problems in aviation construction, and it’s becoming more common because the alternative is unavailable. Airports with constrained airfields can’t keep spreading sideways, so the growth has to go somewhere. Sequencing steel over live gates means every pick is scheduled around an airline’s bank, and every shutdown is negotiated rather than assumed.
The Port set utilization targets of 15% on design and 20% on construction management for women- and minority-owned businesses. Funding came entirely from the Airport Development Fund and airport revenue bonds, with no tax dollars.
The deadline wasn’t arbitrary. Seattle hosts FIFA World Cup matches starting in June 2026, and the concourse opened to passengers ahead of them.
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Project Team & Details
| Owner / Client | Port of Seattle |
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| Architect | The Miller Hull Partnership (design lead) with Woods Bagot |
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| Consultants | Jacobs (Construction Management) |
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| General Contractor | Turner Construction Company |
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| Status | Completed |
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| Delivery Method | CMAR |
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| Sustainability Certification | LEED Silver (pursuing) |
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| Funding Source | Public (Municipal) |
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