As for "any WWII fighter plane", no other fighter of the time had as low a polar inertia as the P39. No other plane had as high a percentage concentration of its mass amidships as the P39, making it the least resistant to rotation in a stall situation of all of them. No other fighter (except possibly the Merlin Mustang in some cases) did as much flirting with its aft CG limit. Both of these features (low polar inertia and aft CG) are stability detractors, increasing both the probability and the severity of a departure in a stall situation. Add to that, the "light" touch on the controls and the jerky overcontrolling of a panicked inept pilot, and you've got a potential deathtrap. Not the type of "honest flying airplane" to instill confidence in nugget aviators and their instructors.