But at Dunkirk it was almost always stationary or slow moving ships or those overload with troops so they couldn't maneuver at will.
During the evacuation, Ju87s attacked only in 2 or 3 days, because of bad weather.
Even so, 9 destroyers were sunk, (6 British, 3 French) despite heavy opposition by the RAF.
My question would be: how many warplanes were actualy used to attack the ships at Dunkirk ?
At Crete again most of the losses occured when the ships were either almost out of or ran out of AA ammo, stopped to help other damaged vessels, or again were over crowded with evacuees.
AA supplies don't last forever - usualy a few hours of shooting for any kind of vessel.
And of course, the volume of AA fire can make for an "X" number of attacking planes. It's one thing to protect a squadron against 12 Ju87, and another against 200.
Even if they manage to pull something out are they going to be in any shape to support the invasion afterwards?
I guess it would depend on the exact operational moves. Aug-Sep 1940 had GErman fighters all over the southern part of Britain - with all the shortcomings attached.
Keeping them just over the channel, or focusing only on the airfields closest to shore would probably reduce the number of lost German planes. (the range problems would be diminished, and damaged planes could land more often back in France, instead of crash landing on British soil, with the pilot remaining prisoner)
And, again, focus is probably key. Shifting the strategy every 2-3 weeks brings nothing good - continous pressure with all 5 luftflottens, and possibly some Italian/Romanian/Hungarian airforce support may well change the balance of power rapidly.