Step 4: final step: the finetuning
as for one reason I can't seem to add those little yellow blocks on my pictures so I'll have to write it here
on pic 1 if you see those gaps across your plane you'll need to mess a little with the outer wings so those gaps are gone cause those make your plane crash instead of gliding.
also on pic 1 if at the end your wing are like this --_ you'll again need to mess a little with it otherwise the plane will not stop spinning
on pic 2 u see that at the end of the plane u have a kind of u form you'll have to check those gaps at the middle of the plane and again mess a little with those to make the wings go completly straight