That's the NATO codename for the Su-37 Super Flanker. It basically is a regular Su-27 with added canards, more power, assymetrical vectored thrust and an all new fly-by-wire system. This makes it one of the most manouverable jet fighters in the world. If you haven't heard of this plane yet and you want to see just how manouverable it is, go see these video's.

In Lock On, there is no Su-37, but the Su-33 with the Terminator skin comes pretty darn close to it. Please enjoy the screenshots.