Sukhoi-Gulfstream S-21 In the early 1990s, Gulfstream Aerospace and the Sukhoi Design Bureau in Moscow, Russia began joint development of a Supersonic Small Business Jet (SSBJ), code named the S-21. Because the market for a supersonic business jet remained questionable, the project was shelved after mounting delays.
Gulfstream eventually dissolved their partnership with Sukhoi, although Sukhoi continued working on the S-21 project. The S-21 would have been capable of a Mach 2+ cruise.
