The P-51 Mustang had 281 kills during WW2. The FW-90 was next with 267. There are stats on this page for German aircraft:
North American P-51 Mustang --- The plane that went all the way. As Allied armies fought their way deep into occupied Europe, it was the P-51 Mustang which wrested control of the skies from the Luftwaffe. More than just a ferocious dogfighter, the P-51 Mustang was one of the fastest piston-engined fighters and could fly higher and go further than any other combat aircraft of the war. The P-51 Mustang claimed the most Allied kills with no fewer than 281 pilots earning the "Aces" (5 kills) distinction in a Mustang. It was the greatest fighter of the war.
Focke-Wulf Fw-190 --- One of the best fighters of all time, no Allied pilot who fought in the skies of Europe will forget the feats of the Fw-190. Introduced in September 1941, this fighter shocked RAF pilots and inflicted cruel punishment to Allied bombers flying over Europe. Highly respected by Allied pilots, the Fw-190 was a superb fighter, fighter-bomber and anti-tank aircraft. Oberleutnant Otto Kittel scored most of his 267 kills in a Fw-190, forever immortalizing him as the fourth top scoring ace of the Luftwaffe.
Supermarine Spitfire --- The Supermarine Spitifre is possibly the most famous combat aircraft in history. Champions of low level duels, Spitfires earned their immortality as the fighter that turned the tide in the Battle of Britain. Against its greatest foe, the Messerschmitt Bf-109, Spitfires forced the German fighter to stay low to protect the bombers - negating the Bf-109s advantage while multiplying its own. After the homeland threat was over, Spitfires served as fighter-bombers and carrier-based fighters, where they served with distinction in all combat theaters. The Spitfire is in the league of one of the best fighters of all time.
Messerschmitt Bf-109 --- Aviation history describes the Bf-109 as one of the greatest fighters in history. When first introduced, this fearsome aircraft was among the best of its day, putting it in the same league as the British Spitfire. Fast and graceful, Bf-109s ruled the skies at high altitudes, but as bomber escorts over Great Britain, these high flyers had to pitch their battles at low altitudes - a task it was ill-suited to perform. Nevertheless, the Bf-109 with its heavy punch of 20mm cannons would go on to become the most important fighter in the Luftwaffe, serving on all fronts of the war.
Junkers 87 Stuka --- At least until 1942, the high pitched scream of the Stukas sent troops beneath scurrying for cover. As dive-bomber, and ground attack aircraft, it was deadly accurate and excelled in its role as an anti-tank aircraft. Rugged and cheap, a formation of Stukas struck fear even in the hearts of seasoned veterans. Hans-Ulrich Rudel, the top scoring Luftwaffe ace destroyed over 500 Russian tanks - that's five Russian tank corps. Stalin placed a price on his head, but it was never claimed. Stukas lost their invincibility when the Allies had air cover, as Stukas were very vulnerable to enemy fighters.
Messerschmitt 262 --- The Messerschmitt-262 makes it into this list not because of the impact it had on the war, but because of the contributions it had made after the war. Using its secrets in rocketry and airframe design, scientists developed more advanced aircraft prototypes up to the speed of Mach-1. There is no doubt that the Me-262 was revolutionary and should German industries be capable of producing the much needed numbers, the Luftwaffe would once again have achieve air superiority. When first introduced in September 1944, there was no fighter in the Allied arsenal which could match it in an air duel.
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