Lindbergh’s Spirit of St. Louis hangs in the National Air & Space Museum. (Photo by Michael S. Williamson/The Washington Post)

The Smithsonian will begin an almost $1 billion renovation of the National Air and Space Museum next summer with the closing of the western side of the building, officials announced Wednesday.

Museum officials are waiting for Congress to provide funding for the first part of a seven-year, $650 million renovation that will be completed in stages to allow the city’s most visited museum to remain open. Smithsonian Secretary David Skorton said officials are cautiously optimistic that their request will be granted, but he said it is unclear if the project will move forward without it.

The renovation will be the most expensive capital project undertaken by the museum complex, with a price tag almost double the construction of the $540 million National Museum of African American History and Culture.

The project includes new mechanical systems for the building, which opened in 1976, and the replacement of its marble exterior. In addition to the $650 million in federal aid, the Smithsonian has pledged to raise $250 million in private donations to update the galleries.

The west side of the building houses nine exhibitions. Most of the objects on view in these galleries will be moved to a new collections storage space at the Steven F. Udvar-Hazy Center in Chantilly, Va. The federal government last year appropriated $40 million for the facility, and the museum has requested $10 million more. The storage space is expected to be ready by 2019.

During construction, many of the museum’s most popular artifacts, including the Wright flyer, the Spirit of St. Louis and the Mercury Friendship 7 will remain on view. The museum attracts about 7 million visitors annually.

Officials expect new exhibitions to open starting in 2021.