public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
if ((newkeys & KEY_JUMP))
{

SetPlayerVelocity(playerid,0.0,0.0,0.10);
}

}

и еще чтобы в машине по нажатию клавиши 2 взлетал:

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
if ((newkeys & 512))
{
new Float:x, Float:y, Float:z;
GetVehicleVelocity(GetPlayerVehicleID(playerid), x, y, z);
SetVehicleVelocity(GetPlayerVehicleID(playerid) ,x ,y ,z+0.3);
}
return 1;
}