From "Flying Guns World War II. Development of Aircraft Guns, Ammunition and Installations 1933-45. By Anthony G. Williams and Emmanuel Gustin":
"The ineffectiveness of air attack against tanks should have caused no
surprise because the weapons available to the fighter-bombers were not
suitable for destroying them. Put simply, the heavy machine guns and
20 mm cannon were capable of hitting the tanks easily enough, but
insufficiently powerful to damage them, except occasionally by chance.
The RPs and bombs used were certainly capable of destroying the tanks
but were too inaccurate to hit them, except occasionally by chance."
You may also take a look at "Allied Fighter-Bombers Versus German in North-West Europe 1944-1945: Myths and Realities" by Ian Gooderson, published in Journal of Strategic Studies. 1991, vol. 14, No. 2. Coming basically to the same judgements.
BTW, fighter-bomber pilots claimed MUCH more enemy tanks destroyed than the actually did:
"The evidence gathered by the OR teams indicated that very few tanks
were destroyed by air attack. A British War Office analysis of 223
Panther tanks destroyed in 1944 revealed that only fourteen resulted
from air attack (eleven to RPs and three to aircraft cannon). During
the Mortain battle of 7-10 August, the RAF and USAAF launched
sustained attacks on a German armoured column over a period of six
hours, claiming 252 German tanks destroyed or damaged in nearly 500
sorties. It was subsequently discovered that there had only been a
total of 177 tanks or tank destroyers deployed by the Germans and just
46 of those were lost, of which only nine could be attributed to air
attack (seven to RPs and two to bombs). During the German retreat from
the Falaise pocket later in August, the RAF and USAAF claimed 391
armoured vehicles destroyed. Shortly afterwards, the battlefield was
examined and only 133 armoured vehicles of all types were found, of
which just 33 had been the victim of any sort of air attack."
Source again: "Flying Guns World War II"
