How do I complete story mode on learn to fly 3 (I am talking about the 4,000,000 meters high)?

A bit of backstory: I have finished every other mode along with the initial story mode that you have to do when you start the game. After all that, I decided to play story mode again, only this time I am flying to the height of 4,000,000 meters. However, I just can’t seem to get there. I have Max level on all the boosters, stages, launcher, and body. Even with that, I can only get to a height just over 1,000,000 meters. How do I get to 4,000,000 meters? Do I need a particular bonus shop item or something?