Y, Y, X, B, A, LB, LB, Down, Up
You typically need to use a third-party keyboard app or a controller to input "JUMPJET." Why the Hydra? San Andreas Fighter Jet Cheat
By toggling the thrusters (Right Stick forward/backward or Num 8/2 on PC), you can hover like a helicopter. Y, Y, X, B, A, LB, LB, Down,