New entranceways will be among the updates. (Artist’s rendering courtesy of the National Air and Space Museum)

Starting in the summer of 2018, the National Air and Space Museum will get such a complete makeover, while remaining open to visitors, that it will take seven years to complete. Revamping the exterior, adding new entrance structures, and updating or redoing all 23 galleries will come with an expected price tag of $900 million.

“Transformation of exhibitions begins a new era for the museum,” Gen. J.R. “Jack” Dailey, the director of the National Air and Space Museum, said in a statement.

The Smithsonian will conduct the work in two separate stages so guests will still be able to visit.

In 2016, it was the second-most visited museum in the world in 2016, and a total of 350 million have come through its doors since opening in 1976. The heavy traffic has taken its toll, and parts of the museum certainly still feel like they would have been cool in the 1970s (in other places, they’ve caught up with the times).

The first stage of work will begin on the west side of the building. Most of the artifacts in the nine galleries of that wing will be moved to a new storage facility near Steven F. Udvar-Hazy Center while the construction is underway.

The renovations will dwarf previous efforts, like the recently revamped “Boeing Milestones of Flight Hall.” Some exhibitions will be completely replaced, while others will keep the same themes with updated materials. Visitors will start seeing the new exhibitions roll out in 2021.

“The icons people associate with the National Air and Space Museum are as inspiring today as they were when they made history,” said chief curator Peter Jakab. “But through stimulating new exhibition techniques and innovative digital engagement, we will tell exciting and relevant stories in ways that resonate with our modern communication-savvy world.”