The National Air and Space Museum (NASM) of the Smithsonian Institution holds the largest collection of historic aircraft and spacecraft in the world. It was established in 1976. Located in Washington, D.C., United States, it is a center for research into the history and science of aviation and spaceflight, as well as planetary science and terrestrial geology and geophysics. Almost all space and aircraft on display are originals or backups to the originals. It is the second-most popular of the Smithsonian museums and operates an annex, the Steven F. Udvar-Hazy Center, at Dulles International Airport. The museum currently conducts restoration of its collection at the Paul E. Garber Preservation, Restoration, and Storage Facility in Suitland, Maryland.