Yay. Glad you worked out the problem. :) @TheSpaceViking

@jamesPLANESii I figured it out (I think). There was a larger amount of drag on the front of the aircraft than on the back. I’ve had this problem when I designed rockets in simple rockets 2. I added some more stuff to the back of the plane and it now flies fine.

git gud

Ok so here’s the situation.
Imagine you’re going really slow, and are about to stall. What do you want to happen to the plane? Do you want it to:

1. The nose to drop so when it breaks away you gain airspeed And the stall is recovered?
2. Stay level, with the attitude of the stall getting even worse, causing it to be unrecoverable?
3. The plane to pitch up even further causing a hyper, unrecoverable stall every time you pitch?

The answer is obviously 1. So, noting that the lift force is the supporting force, going upward, and that the weight force is the force going downward, how do you reckon you’d make the nose go lower when you stall?

You might want to read the in-game tutorials

If you publish the plane I can take a look at it, this will usually happen if the center of mass is behind the center of lift.