The National Air and Space Museum of the Smithsonian Institution , also called the Air and Space Museum , is a museum in Washington, D.C. It was established in 1946 as the National Air Museum and opened its main building on the National Mall near L'Enfant Plaza in 1976. In 2018, the museum saw approximately 6.2 million visitors, making it the fifth most visited museum in the world , and the second most visited museum in the United States. The museum contains the Apollo 11 command module , the Friendship 7 capsule which was flown by John Glenn , Charles Lindbergh 's Spirit of St. Louis , the Bell X-1 which broke the sound barrier , the model of the starship Enterprise used in the science fiction television show Star Trek: The Original Series , and the Wright brothers ' airplane near the entrance. The National Air and Space Museum 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 the original backup craft. It operates an annex, the Steven F. Udvar-Hazy Center , at Dulles International Airport , which opened in 2003 and itself encompasses 760,000 square feet (71,000 m2). The museum currently conducts restoration of its collection at the Paul E. Garber Preservation, Restoration, and Storage Facility in Suitland, Maryland , while steadily moving such restoration and archival activities into the Mary Baker Engen Restoration Hangar, a part of the Udvar-Hazy annex facilities as of 2014.