Mitch, do a little reading about the Royal Navy's heroic efforts to resupply Malta. Despite the British having air cover from both carriers and airbases on Malta, the German and Italian attackers sank more than half of the british vessels, and only when they were completely under the umbrella of the land based aircraft from Malta were the surviving ships able to make it into Malta's harbor. The German and Italian aircraft were attacking from air bases in North Africa and Sicily, and had only a very limited time over the target.
Imagine what would have happened to the British vessels approaching Malta if there were little or no RAF or Fleet Air Arm aircraft attempting to protect them, and if the German and Italian aircraft were taking off from airbases only a few miles from the ships.
Now place the vessels in the liited confines of the English Channel, and have them coing up against the Bismark, Scharnhorst and Prince Eugen, as well as countless E-Boats and U-Boats protecting the German barges, but only after getting past a swarm of ME 109's, ME 110's, Stukas, Heinkel HE 111's, Dornier flying pencils, et al.
Then ask yourself, what would have happened to the Allied fleet off Normandy if the Nazis, rather than the Allies, had complete air supremacy.
All I can say is I sure am glad we never had to find out if the Royal Navy could have taken on the German fleet and the Luftwaffe without air support.{sm2}