With the ongoing debates about UAPs, a basic question is just how reliable reports of sightings are. And it occurs to me that we had the perfect laboratory for that question during World War Two. The airspaces of the belligerent powers were indeed being penetrated by foreign craft, and swiftly and accurately identifying the same was a matter of national survival. And like virtually everything else of conceivable impact on the war effort, observer reliability and performance was doubtless studied and analyzed in every possible way by experts.
So does anyone know about the outcome of any such studies? Did they for example show that untrained civilian reports were notoriously unreliable, prone to hysteria and error? Was the planet Venus or weather balloons routinely reported as enemy bombers? Did the government have to compile a list of “known crackpots” whose reports were deemed worthless?
Bear in mind that bombers and planes at WWII altitudes were audible from ground level, moving fast, almost always in a formation with other aircraft, and in daylight had an easily observable silhouette, and did not emit light. The chances of someone reporting Venus or a weather balloon as a bomber or fighter would be all but nil. I’ve certainly heard of many false reports in the sense that someone reported enemy aircraft which turned out to be friendlies, but not of reports that turned out not to be aircraft at all.
I’m assuming you’re familiar with the phenomenon of foo fighters during WWII when unidentified lights were spotted by Allied aircrew on night operations.
In addition to the issues @Princhester noted, nations didn’t rely on reports of untrained civilians to give warning of approaching enemy aircraft, they relied on both radar which was in its infancy in many ways but could reliably detect formations of aircraft and on trained civilians. A couple of examples of these would be the British Royal Observer Corps which played an invaluable role in the Battle of Britain, and the Coastwatchers who were equally invaluable at reported the movement of both Japanese planes and ships down the island chain in the Southwest Pacific. Thier radio reports of Japanese bomber flights heading for Henderson Field on Guadalcanal from far up the island chain long before they would be in radar range from Guadalcanal were invaluable in allowing fighters to be launched and reach sufficient altitude to be in position to intercept Japanese bombers once they arrived.
Not a direct answer to your question but a parallel case.
Sceptics of crop circles being anything other than a succession of increasingly elaborate practical jokes have long pointed out that the phenomenon is completely unknown in the historical pictorial record of many hundreds of thousands of images recorded for aerial archaeological survey across Britain since WW2. These images were scrutinised carefully for any suspicious bit of darker soil or shadow that could be suggestive of anything that was not a boring old field. Similarly, millions more aerial images were taken for topographic survey in the same period, but they were probably not all examined with the same intensity.
While this would not make any Crop Circle Believer skip a beat, it completely undercuts one of the main claims as to them being ‘real’ - that they were the products of unique and natural highly localised atmospheric conditions.