NASA X-Plane
The first experimental jet built by NASA in more than a decade, the X-Plane aims to break the sound barrier without the loud thunderclap that has sidelined supersonic planes from commercial use since 2003. NASA signed a $247.5 million contract with Lockheed Martin to build the X-Plane and will achieve nearly silent supersonic travel with a uniquely-shaped hull which sends the shockwaves away from the jet and prevents them from coming together in loud booms. The proposed aircraft will be 94 feet long with a wingspan of 29.5 feet and is expected to be delivered by the end of 2021.