Alaska Air Group will unveil plans and break ground Thursday on a new building between its corporate headquarters and flight training center in SeaTac.

The building is the first phase of the code-named Project Copper River, which the Business Journal first reported in December. Two weeks later Alaska paid nearly $32 million for the approximately seven-acre property at 19225 International Blvd.

Both times Alaska officials declined to comment, but on Tuesday the company announced it will host the Thursday groundbreaking that it said represents “the next chapter for (its) presence in its hometown.” Gov. Jay Inslee, other dignitaries and Alaska CEO Brad Tilden are scheduled to attend.

Plans on file with the city of SeaTac show that Project Copper River is a four-phase development with four office buildings, each six stories, and totaling 490,000 square feet. The first phase will have a parking garage as well as the office building.

An Alaska spokeswoman was not immediately available to comment Tuesday.

The SeaTac Blog last week reported that Megan Ouellette, Alaska’s managing director of government affairs, briefed the City Council on the project that is south of South 192nd Street between 28th Avenue South and International Boulevard.

The first building and parking garage should be ready for occupancy by late next year or early 2020.

“We are also working with the city to lay the groundwork for the possible later development of the additional three buildings,” Ouellette told the blog.

The expansion comes as Alaska finalizes integrating Virgin America operations into its own. Alaska paid $2.6 billion for the California airline two years ago.

“We are undertaking this project to support our growth and to really accommodate additional employees, including those that are coming over from Virgin America as a result of our acquisition,” Ouellette said.

The first building will be called the Hub and link Alaska’s headquarters on the east side of International Boulevard and the flight training center on the west side of 28th Avenue South. The SeaTac Blog reported that Ouellette said the Hub will not be the headquarters, which will remain at the current location.

The Hub “will be a warm and welcoming facility for employees and guests” and will include space for support functions and will be a recruiting center, said Ouellette. The new structure will also house the airline’s “integrated operations center … the nerve center of operations for the airline.”

The new space will create “a campus-like environment with an active pedestrian feel allowing Alaska employees and guests to safely walk between buildings.”

Three Seattle companies — development manager Seneca Group, architecture firm NBBJ and real estate brokerage Kinzer Partners — are working on Project Copper River.