The history of tactical air power in the battle of Normandy has been fraught with both misunderstanding and contradiction. Largely ignored by the army-centric historians who have written the histories of the campaign, it has been asserted on the one hand that Allied air power was overwhelming and on the other that the system for controlling it was cumbersome and ineffective. On the face of it, at least, there would appear to be some tension between those two schools of thought. Which is more accurate? In order to examine that question, it is important to begin with an understanding of the doctrine for tactical air power—the contemporary doctrine of the time—and disputes about both that doctrine and the role of air power in the campaign. What emerges is that there is enough blame to go around for all parties—and enough credit. In truth, the doctrine of the time was under-developed, and this simply reflected some of the larger doctrinal weaknesses of the Western Allies’ militaries.
Johnston, Paul "Tactical Air Power Controversies in Normandy: A Question of Doctrine." Canadian Military History 9, 2 (2000)