flaps did not act as a speed brake; they affected the pressure distribution in a way that retained the wing's lift. Late in 1943, a few hundred dive flap field-modification kits were assembled to give North African, European, and Pacific P-38s a chance to withstand compressibility and expand their combat tactics. Unfortunately, these crucial flaps did not always reach their destination. In March 1944, 200 dive flap kits intended for the European Theater of Operations (ETO) P-38Js were destroyed in a mistaken identification incident in which an RAF fighter shot down the Douglas C-54 Skymaster (mistaken for an Fw 200) taking the shipment to England. Back in Burbank, P-38Js coming off the assembly line in spring 1944 were towed out to the ramp and modified in the open air. The flaps were finally incorporated into the production line in June 1944 on the last 210 P-38Js. Despite testing having proved the dive flaps effective in improving tactical maneuvers, a 14-month delay in production limited their implementation, with only the final half of all Lightnings built having the dive flaps installed as an assembly-line sequence. Johnson later recalled: Buffeting was another early aerodynamic problem. Distinguishing it from compressibility was difficult, as both were reported by test pilots as "tail shake". Buffeting came about from airflow disturbances ahead of the tail; the airplane would shake at high speed. Leading-edge wing slots were tried, as were combinations of filleting between the wing, cockpit, and engine nacelles. Air-tunnel test number 15 solved the buffeting completely and its fillet solution was fitted to every subsequent P-38 airframe. Fillet kits were sent out to every squadron flying Lightnings. The problem was traced to a 40% increase in air speed at the wing-fuselage junction where the thickness/chord ratio was highest. An airspeed of at could push airflow at the wing-fuselage junction close to the speed of sound. Filleting solved the buffeting problem for the P-38E and later models. Another issue with the P-38 arose from its unique design feature of outwardly rotating (at the "tops" of the propeller arcs) counter-rotating propellers. Losing one of two engines in any twin-engined, noncenterline-thrust aircraft on takeoff creates sudden drag, yawing the nose toward the dead engine and rolling the wingtip down on the side of the dead engine. Normal training in flying twin-engined aircraft when losing an engine on takeoff is to push the remaining engine to full throttle to