The Battle of the Philippine Sea in the Marianas in June 1944 was marked by the destruction of huge numbers of Japanese aircraft with low losses to the United States Navy. The Americans had set up an extensive program, including building a carrier that had no hangar deck, to train both aircrew and deck handlers. American pilots were entering combat with some 600 hours in the air. In contrast, the Japanese were sending green pilots into combat with only 50 hours of flight time and little combat training.
In addition, the Americans had numerical and technological superiority. The Japanese were replacing their aging B5N torpedo bombers with a more advanced version, the B6N Tenzan. It still lacked self-sealing fuel tanks or crew armor. In contrast, the Americans were continually introducing new aircraft. The F4F Wildcat was in service throughout the war, but after 1942 it was used as a ground attack aircraft. It was replaced in the front line carrier squadrons with the F6F Hellcat, which had more powerful armor and could dogfight with the Japanese Mitsubishi Type 00. The Marines were given the F4U Corsair, which was not rated for carrier duty. Flying from forward airstrips, it was very effective against Japanese aircraft.