A supersonic transport aircraft (SST) is a civilian supersonic aircraft. It is designed to transport passengers at speeds greater than the speed of sound. Only two supersonic aircrafts are known till date. These are Concorde and Tupolev Tu-144.

Concorde is a British-French supersonic passenger jet airliner, which was operated till 2003. It had a maximum speed over twice the speed of sound with seating capacity of 92 to 128 passengers. It had first flown in March 1969 on trial. Later it had entered service in January 1976 and thereafter, had retired in the year 2003.

Tupolev Tu-144 is another name of supersonic passenger jet airliner. Its design was a product of the Tupolev design bureau, headed by Alexei Tupolev of the Soviet Union and manufactured by the Voronezh Aircraft Production in Voronezh, Russia. It had conducted 55 passenger service flights. It had last flown in 1994 by NASA.

The prototype had first flown on 31 December 1968 near Moscow, two months before the first fight of the Concorde. This aircraft was introduced into passenger service on 1 November 1977, almost two years after Concorde. In 2016, NASA announced that they had signed a contract for the design of a modern low-noise SST prototype. The designing team is led by Lockheed Martin Aeronautics. Several companies had proposed to bring back supersonic business jet again.

More Info: en.wikipedia.org