Washington, April 4: US space agency SA has started to create a supersonic manned aircraft that may cause no eardrum-battering sonic boom. It announced plans on Tuesday to grant a $247.5 million contract to Lockheed Martin, an American aerospace and defence group to design and build a new plane, Xinhua news agency reported. In this Low-Boom Flight Demonstration contract, Lockheed Martin is obliged to completing the design and fabrication of an experimental aircraft, known as an X-plane.