X-Plane cheats, and Codes for PC.
Enter the weight and fuel section in the settings menu. Set the fuel load to maximum. This will make the fuel tank full again. This can be repeated as needed.
Get into space faster
Pilot the X-15 and use the B-52 drop in Location\Special In-flight. Press [Space] to be released and aim straight up. By the time you are out of fuel, you will be in space.