Fantastic game! Not to say this was a bad thing but I was fascinated when I quickly discovered you can fly backwards. It seems to me that when going up your deceleration can push your speed negative allowing you to fly backwards. I would say this feature makes the game way better. It also makes me wonder for my own projects, what kind of equation could be employed to emulate stall out. Perhaps an exponential decrease in speed plus some extra gravity? IDK. I'll have to see your explanation when you put it out to get a better handle on the physics! Still dumbfounded you made a flight simulator!
ex:
Speed=Speed/2^(Angle/PI)+if(Angle>0){Constant*DownVector/TimeStep}