When NASA purchased the prototype Boeing 737, it was to be used as a support system for a specific research program. The engineers who designed the TCV program did not expect the airplane to be used to test helmet mounted synthetic vision systems, to gather data on flow physics, or to find threefoot wide holes in the sky for the United States Air Force. But in designing a research tool to flight test advanced transport concepts, the NASA and Boeing engineers ended up creating an ideal testbed for a much broader range of technologies and research projects. The TSRV 737 may have begun as a test plane for a single research program, but it evolved into a national resource for airborne research. Like the many wind tunnels at the Langley Research Center, the NASA 737 provided both government and industry with a fully instrumented research facility for gathering data, testing new designs and demonstrating concepts to further aeronautical technology.