First 24 hours of Operation Overlord - loss of 113 aircraft, many by friendly fire.
"6 Jun 1944 See D-Day. Allied air forces flew a total of 14,674 sorties during the first 24 hours of Operation Overlord for the loss of 113 aircraft, many by friendly fire. Fighter cover for the invasion beaches was provided by nine squadrons of Spitfires, while Typhoon and Mustang fighter-bombers of 2nd TAF flew armed reconnaissance missions further inland. Such was the Allied air supremacy that the Luftwaffe only flew 319 sorties in the same period."
http://www.raf.mod.uk/history/rafhis...meline1944.cfm