Instructions
Add weight to the nose. Attach a paperclip or put tape on the nose. The heavier nose will keep the plane from flipping up and back.
Turn the back corner of the right wing down slightly and the back corner of the left wing up slightly if the plane tends to bank to the right during flight. Do the opposite if the plane banks left.
Bend the back corners of both wings up if the plane tends to dive. Bend them down if the plane tends to climb.
Turn the nose of the airplane back as you fold it so the tip will be blunt instead of pointed.
Add a tail. Cut a narrow strip of paper, fold it lengthwise and cut the end to create stabilizers. Insert the other end of the tail into the back of the plane so it lies in the fold. Add weight to the nose to balance the weight of the tail.
Redesign your plane with a mountain fold rather than a valley fold. The fold will not spread apart during flight and your plane will maintain its shape.