I voted for the Battle of Midway because of how badly it crippled the Japanese Navy in such a short time (3 major carriers sunk in 10 minutes or so). It was the most important air battle in the Pacific in my opinion. In Europe, the argument might be made that the airwar during the battle of Kursk (Operation Zitadelle) was extremely important, as it helped turned back the last major offensive operation of the war for the Nazis (not excluding the Battle of the Bulge). The problem with the Kursk airwar is that it happened not over a few days but over a week and a half and the statistics, like so much else about the Eastern Front, seem to be fairly murky and subject to debate. It also involved relatively small tactical formations, not large strategic operations. Still, the Soviet attack aircraft, fighting their way through heavy Luftwaffe opposition, who had to contend with Soviet fighters, inflicted heavy casualties on the German armored units, in addition to suffering heavy losses themselves. As a matter of fact, if anyone has some relatively concrete numbers of the losses on both sides in the Kursk airwar, I'd like to see them.