From Flying Magazine: "In all, an estimated 13,000 Allied aircraft participated in the D-Day operations. It remains the single largest aerial operation in history. As it was an unprecedented action, it was a learning process, and there were fundamental misunderstandings about how aircraft would operate and interact. The operation was so critical and so complex that commanders made clear early on that they were willing to accept great losses in order to establish a beachhead."
From History on the Net: "However, success was not achieved without cost. During June 1944 the Eighth and Ninth Air Forces lost 904 aircraft: 284 in aerial combat, 400 to flak, and 220 operationally. The total included 320 Eighth Air Force B-17s and B-24s plus 44 B-26s and A-20s of the Ninth Air Force. Combined Eighth and Ninth fighter losses amounted to 540 Thunderbolts, Lightnings, and Mustangs."
From Smithsonian Air and Space Museum: "The planners feared friendly fire - anti-aircraft fire from Allied naval vessels and Allied troops - against their own air flotilla, and pilots mistakenly engaging in dogfights against their own comrades in arms. The existing system for identifying friendly aircraft, Identification Friend or Foe, would in all probability be overwhelmed by the sheer number of aircraft over the beaches. To avoid fratricidal incidents, the D-Day planners called for paint and brushes, and ordered that the aircraft of the Allied Expeditionary Air Force and supporting units be painted with alternating black and white stripes on wings and fuselage - 18 inches wide on single-engine aircraft, and 24 inches wide for twin-engined craft. They were called invasion stripes." D-Day stripes article https://airandspace.si.edu/stories/editorial/stripes-d-day
From Wikipedia: "CG-4As went into operation in July 1943 during the Allied invasion of Sicily. They were flown 450 miles across the Mediterranean from North Africa for the night-time assaults such as Operation Ladbroke. Inexperience and poor conditions contributed to the heavy losses. They participated in the American airborne landings in Normandy on 6 June 1944, and in other important airborne operations in Europe and in the China Burma India Theater. Although not the intention of the Army Air Forces, gliders were generally considered expendable by high-ranking European theater officers and combat personnel and were abandoned or destroyed after landing. While equipment and methods for extracting flyable gliders were developed and delivered to Europe, half of that equipment was rendered unavailable by certain higher-ranked officers. Despite this lack of support for the recovery system, several gliders were recovered from Normandy and even more from Operation Market Garden in the Netherlands and Wesel, Germany."