U.S. Navy and Marine F6F pilots flew 66,530 combat sorties and claimed 5,163 kills (56% of all U.S. Navy/Marine air victories of the war) at a recorded cost of 270 Hellcats in aerial combat (an overall kill-to-loss ratio of 19:1 based on claimed kills). Claimed victories were often highly exaggerated during the war. Even so, the aircraft performed well against the best Japanese opponents with a claimed 13:1 kill ratio against the A6M Zero, 9.5:1 against the Nakajima Ki-84, and 3.7:1 against the Mitsubishi J2M during the last year of the war. The F6F became the prime ace-maker aircraft in the American inventory, with 305 Hellcat aces. The U.S. successes were not just attributed to superior aircraft – from 1942 onwards, they faced increasingly inexperienced Japanese aviators and had the advantage of increasing numerical superiority. In the ground-attack role, Hellcats dropped 6,503 tons (5,899 tonnes) of bombs.