SEA's $399 Million Concourse C Expansion Brings a Plane Spotter's Dream Terrace and Much More to Seattle

Seattle-Tacoma International Airport is on the cusp of one of the most significant transformations in its history. With the FIFA World Cup arriving in Seattle on June 15, 2026, the Port of Seattle is racing to complete a sweeping $399 million expansion of Concourse C that will nearly triple the building's size, introduce a raft of new dining and retail options, and, most notably for aviation enthusiasts, deliver a rare and dedicated plane spotter terrace with unobstructed views of an active airfield.

Building Up, Not Out

SEA Airport is one of the most space-constrained airports in North America, operating on a mere 2,500 acres of land and not going beyond those limits, so the airport is building up instead of out. The C Concourse Expansion is the architectural embodiment of that strategy, and it is a bold one.

The expansion stacks four new floors on top of the existing C Concourse, boosting the footprint from roughly 81,000 square feet to about 226,530 square feet and organising the space around a tiered marketplace anchored by an amphitheatre called the Tree at C. Turner Construction is the general contractor on the roughly $399 million expansion, which hit a topping-out milestone late last year when one of the final steel beams was set in place. Miller Hull and Woods Bagot are the design partners.

Substantial completion for construction is projected for Q2 2026, ahead of the 2026 World Cup Tournament. Funding for the project will come from a combination of Airport Development Fund and future revenue bonds. As with virtually all airport projects, no taxpayer dollars will be used to fund the project.

The Lookout at C

The centrepiece for aviation enthusiasts is the glass-encased observation deck known as the Lookout at C. It is a glassed-in observation area, looking west-southwest from the C Concourse toward the main terminal and the airport's taxiways, some of the gate areas, and SEA's three runways. 

SEA Airport Managing Director Lance Lyttle described it succinctly: 

 

"This concourse will be a planespotter's dream, with the Lookout at C providing views of the airfield and the Olympic Mountains beyond." 

A public lookout on the third floor is a secure outdoor space that connects passengers with the sights and sounds of an active airside environment, while the Grand Stair seating area overlooks a live performance venue. The terrace is available to all ticketed passengers, a meaningful distinction at a time when observation decks at major U.S. airports remain a relative rarity.

The space will also be temperature-controlled to provide views without exposing plane spotters to the variable weather of the Pacific Northwest.

A Marketplace Rooted in the Pacific Northwest

The new C Concourse expansion will welcome passengers to an active, daylight-filled, two-story market that will become a destination for frequent local travellers and a quintessential Northwest experience for all visitors. 

The list of new restaurants is noteworthy: Bell St. Landing by Hudson; Nanny's BBQ; Bite Society; Olympia Coffee; Buffalo Wild Wings Go; Port of Subs; Chills; Seattle Macaron Co.; Great State Burger; and Wanderlust. Port of Seattle Capital Project Manager Adam Olson described the atmosphere the space aims to create: 

"This is a place where people can sit… they can eat. We'll have music across the way. A lot of the local musicians you see in other parts of the port will be performing there." 

Art installations will thread throughout the concourse, including multiple video walls, an art wall, and a "Lookout at C sculpture." 

A Record-Breaking Alaska Airlines Lounge

The expansion includes an all-new, more than 20,000-square-foot Alaska Airlines Lounge. The scale of this facility is remarkable. Alaska Airlines' head of real estate, Ben Brookman, explained the dual purpose of the space: 

"There'll be two components of the lounge, one is the traditional Alaska lounge. We're going to up-level everything, so it's going to be really cool. But then we also need to have a space for the international traveller." 

Passenger Amenities and Sustainability

Beyond dining and the observation deck, the expanded concourse brings a comprehensive set of passenger amenities. The project spans the C and D Concourses with an Interfaith Prayer and Meditation Room, a Nursing Suite, and office space for airport businesses, airlines, and the TSA. 

On the environmental front, the C Concourse Expansion will be the airport's greenest building yet, with all-electric systems powering heating, hot water, and even tenant cooking equipment. SEA was originally pursuing LEED Silver certification but is now going for LEED Gold. The project team made conscious design decisions to augment the existing structure, reusing 62% of the existing structure, thereby minimising the embodied carbon investment of new construction.

Part of a Broader $5 Billion Vision

The C Concourse Expansion does not stand alone. The project is part of the Upgrade SEA suite of capital projects, improving the overall customer experience at SEA. Upgrade SEA will invest nearly $5 billion in projects over the next five years.

Port of Seattle Commission President Sam Cho set out the dual purpose of the investment: 

“This is an exceptional project in terms of elevating the customer experience. However, customer experience is not the only reason why we take on these major projects. The expanded concourse will expand opportunities for local businesses and support the financial stewardship of the airport by increasing revenue opportunities. The whole time, we build with intention by focusing on sustainability and ensuring that our construction expands opportunities through the entire community.”

For an airport that set an all-time passenger record of 52.7 million travellers in 2025, the pressure to deliver this expansion ahead of the World Cup is immense, and for aviation enthusiasts heading through SEA this summer, the reward of watching aircraft from a glass terrace high above one of the West Coast's busiest airfields will make the wait thoroughly worthwhile.