Just as the title says. All three planes that I've made so far have this problem and it makes them very hard to use for dogfighting. To get a better idea of what I mean download one of them, then fly around using the cockpit camera and watch what happens to it after trying to slightly adjust pitch.
Well, just build an aircraft with 1:1 directional stability ratio between yaw and pitch
@AstleyIndustries That makes it way worse.
@MasterManufacturing said it right. In the real world, the F-117 Nighthawk (The stealth fighter) has its CoL and CoG in virtually the same place. The only way it's controllable in flight is thanks to computers constantly correcting for the wobble. Since we don't have flight control systems like that in Simple Planes, compensate by getting your CoG out in front of your CoL.
Add more vertical stabilisers?
Get the CoM further from the CoL, the further the CoM is from the CoL the more stable a plane is.