@Bas: The flight model of this mod is tweaked toward "fun" vs "realistic". Like the helicopters that am told resemble flying RC's, it's possible these jets model has taken ideas from very light planes. I recall as a kid doing paper planes from A4 sheets and I saw similar phenomenom - if the paper plane drops at low speed and gains speed while dropping, the increase in air flow under the paper wings can cause enough lift to make it go up just before hitting ground. This tweaked model is only active when no one is piloting the plane or when it's destroyed mid-air. (It tends to fly more straight when you are piloting even if you don't have any throttle as far as I recall)