The unusual appearance of the P-38 for some reason led me to believe it was an innovation of the latter stages of the war based on engineering developed through analysis of combat experience. Wrong again, Homer.
This period produced quite a few new aircraft, judging by the number of maiden flights you have documented here. It makes me think of the aviation craze that went on last summer, with intensive coverage of things like the Howard Hughes flight, Wrong Way Corrigan, and a host of lesser stories. For a while there you could find an aviation story on page 1 on any given day. I guess it all paid off once the military got serious about buying aircraft. Or should I say when Congress got serious about buying aircraft for the military.
It definately looks like there were a lot of things on the drawing boards for sure. It really makes me wonder where the German aircraft disigners were at at this point since the 109 was already a production aircraft and as we know the Germans produced some very advanced aircraft late in the war. (i.e. Was the Me-262 already in its concept stages at this point).