The fastest jet in the world is NASA X-43 but is an experimental plane. The scramjet design was able to reach a speed of Mach 9.6, or 11,854 Km/h and only three planes were built for it. NASA spent over 230 million us dollars for the spam of 8 years doing all three planes. The NASA x-43 all three planes were an unpiloted aircraft. NASA x-43’s first flight was on June 2, 2001and the last flight was on November 16, 2004. The companies that came up with the idea were ATK GASL and Boeing were responsible for the x-43 development and fabrication of the x-43.NASA made the x-43 because to develop a hypersonic aircraft powered by an air breathing engine.