1. become any type of hellicopter but not the chopper or stealth chopper.
2. in tranquility go to the tallest building and fly up it.
3. land ontop and transform into robot.
4. transform into hellicopter again but hold b.
5. transform into robot and if you make any cracks start again from 4.
6. when you have transformed from hellicopter to robot start presing a and dont press anything else or you will automatically jump and fall.
7. now you are walking on air