I have seen some very questionable videos about WW2 aircraft on Youtube but I watched one tonight that seems to have some new information.
We have all heard about the P-38's compressibility problem and how the "dive flaps" ultimately solved it, but according to the video a different approach was developed in the fall of 1943. A P-38 pilot dove after a German fighter and got into compressibility. Luftwaffe pilots had learned to dive quickly away when bounced by P-38's at altitudes of 18,000 ft and above but to use a shallow angle to trick the P-38's int entering the compressibility regime. Desperate to do something to regain control of the airplane, the P-38 pilot tried shutting down his Right engine. To his amazement he found that he regained control and that he could actually speed up, to over 500 mph, and catch the German fighter he was diving after, and shot it down. Then he restarted the engine at 12,000 ft and went home.
Back home he reported on this approach and was told he was nuts. Then they found out it worked. Over the objections of the maintenance personnel, who were appalled by shutting down an engine in dive and then restarting it, a procedure for the technique was developed and published in March 1944. The Germans eventually found out about it from a captured P-38 pilot and revised their tactics accordingly. It was still used in the ETO until the end of the war.
Never heard about this before!