Tunnel The Unitary Plan Wind Tunnel (UPWT) was completed in 1956 at a cost of $27 million under the Unitary Plan Act of 1949. Since its completion, the UPWT facility has been the most heavily used NASA wind tunnel. Every major commercial transport and almost every military jet built in the United States over the last 40 years has been tested in this facility. Mercury, Gemini, and Apollo spacecraft, as well as Space Shuttle models, were also tested in this tunnel complex. National Full-Scale Aerodynamics Complex (NFAC) Ames Research Center also houses the world's largest wind tunnel, part of the National Full-Scale Aerodynamic Complex (NFAC): it is large enough to test full-sized planes, rather than scale models. The complex of wind tunnels was listed on the National Register in 2017. The 40 by 80 foot wind tunnel circuit was originally constructed in the 1940s and is now capable of providing test velocities up to . It is used to support an active research program in aerodynamics, dynamics, model noise, and full-scale aircraft and their components. The aerodynamic characteristics of new configurations are investigated with an emphasis on estimating the accuracy of computational methods. The tunnel is also used to investigate the aeromechanical stability boundaries of advanced rotorcraft and rotor-fuselage interactions. Stability and control derivatives are also determined, including the static and dynamic characteristics of new aircraft configurations. The acoustic characteristics of most of the full-scale vehicles are also determined, as well as acoustic research aimed at discovering and reducing aerodynamic sources of noise. In addition to the normal data gathering methods (e.g., balance system, pressure measuring transducers, and temperature sensing thermocouples), state-of-the-art, non-intrusive instrumentation (e.g., laser velocimeters and shadowgraphs) are available to help determine flow direction and velocity in and around the lifting surfaces of aircraft. The 40 by 80 Foot Wind Tunnel is primarily used for determining the low- and medium-speed aerodynamic characteristics of high-performance aircraft, rotorcraft, and fixed wing, powered-lift V/STOL aircraft. The 80 by 120 Foot Wind Tunnel is the world's largest wind tunnel test section. This open circuit leg was added and a new fan drive system was installed in the 1980s. It is currently capable of air speeds up to . This section is used in similar ways to the 40 by 80 foot section, but it is capable of testing larger aircraft, albeit at slower speeds. Some of the test programs that have come