The problem is with the wings and landing gear, the normal wings in the game encounter errors at high speeds, so I used a structural wing instead, so the balance of the plane was solved. The second problem is the places where the wings are attached, the wings are connected to the part to which the landing gear is attached, which causes errors that I cannot understand, so I connected the wings to another place and the problem was solved, but a new problem arose. When you mirror the plane, mirror only the part you want to mirror, not the whole. Another problem is that the wing surfaces are too large, which creates balance problems, I made the wing surfaces smaller, I cannot say that the plane flew very well, but most of it was solved Note: During the test flight, the plane is damaged due to the landing gear, I fixed it, if you encounter another error, you can let me know. Good luck