The museum has many rare and important aircraft and other exhibits, including one of four surviving Convair B-36s, the only surviving XB-70 Valkyrie, and "Bockscar"–the B-29 Superfortress that dropped the second atomic bomb in World War II. In contrast to the Smithsonian Institution's National Air and Space Museum, nearly all of the museum's exhibits are extremely accessible. Most are easily touched, even investigated, by visitors.