Enable the "JIH345" code, then play at the free ride area "Rock Quarry". When you start, do a 180 and go down the big ledge towards the container jump. Clear it, then hold it pinned. As you approach the excavator, jump and keep holding it pinned. Jump it as close to the wall as possible. When you are airborne, whip it to the right (towards the wall) and hold it. You should fly over the wall and into a glitch where everything turns white. You will fall for some time, then respawn on the ground with the game stating that you have jumped up to 1,000 feet (usually in the 900 feet range).