Why didn’t they use Air Strikes on the beach in Normandy on D-Day?

You may be interested in several of these old posts by myself and other flairs.

The crux of it is. Why do you think there were not attacks on the beach defenses from the air?

The final softening up of German beach defenses was a combined arms effort by naval artillery by battleships, cruisers, destroyers, and modified landing craft, in conjunction with aircraft. Starting early morning on the 6th, heavier vessels were tasked with suppressing larger German coast artillery batters(as these were the only guns that could threaten the invasion fleet), while smaller vessels targeted the beach defenses themselves as best they could.

Aircraft also contributed to this effort, with a final wave occurring in between the ending of the shore bombardment and before the first landing craft hit the beach, with the first strikes have occurred hours before overnight across Normandy along with the airborne drops. But in the end precision is difficult to achieve on that large a scale, and missing a strong point by even a few yards means you might as well have missed by a mile. A number of factors contributed to this beyond simple error, low cloud cover, crowded airspace, and fear of friendly fire were all present.

While other aircraft were supporting the effort by attacking points inland, be it gun positions, C3 points, and targets of opportunity. And even more were on standby to support elsewhere or hamper efforts to reinforce the combat area.

Bu as to specifically why there was not some prolonged period of bombardment(as you see many times in the Pacific), it comes down to priorities. The bombardment by sea and air was not meant to obliterate beach defense, soften them up sure, but much more it was to immobilize and shock the defenders to slow reactions to the landing. But in those cases the US and Allies had all the benefits of time, there was no way in many cases for Japan to reinforce the garrison without first defeating the US carrier forces screening the invasion, and following the Philippine Sea in 1944(which was triggered by the US landings on Saipan ) even this option was off the table as the IJN had lost virtually their entire carrier fleet, and a good number of their surface combatants as well.

In this case them it was more important to inflict that shock, get troops ashore, and build a bridgehead, before German commanders up and down the chain could recover and effect a real response and draw on reinforcements. A days long bombardment would also have made pointless the weeks and months of deception efforts as to the real landing location, by striking fast and getting ashore the issue could be forced before German leadership had formed a clear picture out of fragmentary reports. While overwhelming naval support, what was thought to be sufficient amphibious armor support, and well equipped landing forces would be able to breach the immediate beach defenses and allow for bridgeheads to be formed and consolidated while linking up with the airborne troops and other beaches.

And remember it worked, on 4 of the 5 beaches troops were ashore within a few hours, and by early afternoon even OMAHA was essentially secure. Then except for an afternoon attack between JUNO and SWORD by the 21st SS Panzer division enemy forces were not threatening the beaches themselves and while some like OMAHA were behind schedule, other areas were on track, and resupply and reinforcements could be brought over the beach unimpeded.