I'm trying to add flight physics to a 3d game. When I try to calculate drag I sometimes get a force that pushes the aircraft backwards if I make the wingspan very large (for example). I have set up a simple scenario: A flat rectangle sheet falling down due to gravity. If I make the gravity force artificially low, or the size of the sheet very large (and light), then the drag force is so large that it actually pushes the sheet upwards. The formula I am using is: drag = dragCoefficent * 0.5 * airDensity * (velocity ^ 2) * sheetArea (dragCoefficent is sheetArea * 1.05) Just by looking at the formula I can see that if you make the area large enough then the force will be huge and counteract gravity to such a degree that the object goes upwards, rather than tends towards zero velocity. So what happens if you are on a planet with very low gravity and drop a large, light sheet of metal from a height? Assuming the sheet stays horizontal you would assume it just falls extremely slowly. Yet the formula doesn't seem to reflect that. Am I missing something obvious or is it perhaps the wrong formula? I want the ability for users to change the scale of drag, gravity etc. with a multiplier. But maybe that is a silly idea because that is what produces this problem in the first place?