The final budget for the C Concourse Expansion Project at Seattle-Tacoma International Airport, amounting to $399 million, was finally approved by the Port of Seattle Commission on September 26. Once the project is completed, it will use solar electricity and run without fossil fuels. It aims to receive a LEED v4 Silver certification. 

The Port of Seattle Commission approved an additional $213 million to the previously approved $185.1 million for the Concourse Expansion Project. The commission approved raising the budget to $399 million with a 5-0 vote.

Adding four levels to the building's existing three floors will change the area where C and D Concourses converge. The project will also add a new dining and retail area, premium lounge space, an interfaith prayer and meditation room, a nursing room, an outdoor viewing area, one story of office space, and three floors of new public space for customer service amenities. The C concourse will also have a place for live performances.

According to Sam Cho, the president of the Port of Commission, "This is an exceptional project in terms of elevating the customer experience." Cho added, "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."

Lance Lyttle, the managing director of SEA Airport, said, "The C Concourse Expansion project is key to establishing SEA's future as a five-star airport." According to Lyttle, by increasing the number of dining and shopping options, the C Concourse Expansion will provide more of what visitors want. "The project also offers more of what our guests love about SEA, like public art, musical performances, sensory room, and great gathering spaces. This Concourse will be a planespotter's dream, with the Lookout at C providing Mountains beyond."

To ensure that the C Concourse Expansion project meets the port's mission to be the greenest and most energy-efficient port in North America, the project is also the first at SEA Airport to include the Sustainable Evaluation Framework. A solar photovoltaic array will also be installed on the roof, and the design will use materials with low embodied carbon and healthy materials. 

A high-performance air delivery system will be installed within the building to improve the overall indoor air quality, and biophilic design elements will also help guests feel more connected to nature. 

Being one of the most space-constrained airports in North America, SEA Airport's growth strategy heavily emphasizes building up to develop amenities and tenant spaces. 

The SEA first used its "build up" strategy at the new N Concourse, international arrivals facility, and renovated or modernized Central Terminal. The "build-up" strategy is also used in the ongoing SEA Gateway Project in the ticketing sector. 

Nearly 45.9 million people accessed the airport in 2022, 11?wer than the 49.1 million people who visited the airport in 2019. In 2024, the SEA airport anticipates having the same amount of travelers as before the pandemic. According to the commission's project memo, the C Concourse Expansion Project will generate $21 million in non-airline revenue by 2031.

The C Concourse Expansion project is anticipated to be substantially finished in 2026.