The Russian Su-27 and Su-30 is touted as a superior fighter because of its better mobility. The SU-27 is alleged to be the first aircraft to perform the cobra maneuver. This is accomplished by having the aircraft's nose pitching up to the vertical while continuing forward and gaining limited additional altitude but slowing the forward motion. The aircraft finishes the maneuver by dropping the nose back to the horizontal and continuing forward. Whether this is actually a valuable combat maneuver is much debated in the fighter pilot community. U.S. test pilots assert that only an expert pilot can carry out the cobra, and that it is only used at air shows and sales demonstrations.
The Russians admit, to those who buy Su-30s, that to perform the Cobra, pilots have to fly a lot and, of course, not every pilot has the right stuff to do fancy maneuvers. That appears to have shut up users, who either don't want to pay the big bucks to have their pilots achieve those levels of excellence, or simply keep silent to avoid embarrassment.