To reach high speeds in excess of 2,000 knots, even to 3,000+ choose any plane, preferrably not a F-117A or A-10A, and go to about 30,000 feet. Then start rolling to the side by pressing and hold the directional key, or using your joystick by holding it to the right or left, to the side on full afterburner, as you keep spinning your nose should start pointing downwards, keep spinning and your speed can reach into the thousands. Sometimes the display stops at 998 Knots, but you are going faster anyway. This may make you plane shake but it can still be maneuvered. Going to very high altitudes through this method can cause your plane to go into a flat spin, which you won't be able to get out of. To speed up the whole process, press "C" to times to increase speed to 4X.