High Speed Civil Transport
The High Speed Civil Transport (HSCT) was the focus of the NASA High-Speed Research (HSR) program, which intended to develop the technology needed to design and build a supersonic transport that would be environmentally acceptable and economically feasible. The aircraft was to be a future supersonic passenger aircraft, baselined to cruise at Mach 2.4, or more than twice the speed of sound.
Source: Wikipedia — High Speed Civil Transport (CC BY-SA 4.0)