Type "bgry" while playing. The screen will freeze and red writing will appear. Press [cursor up] to fly quickly forwards or [cursor down] to fly quickly backwards.
Before take-off or while in flight, press [Y]. Then, press [F4] to increase altitude, [F3] to decrease altitude, [F2] to move forward, and [F1] to stop. The cursor keys may also be used to move the aircraft. Press [Y] to resume normal flight.