Note the side view of the B-17G in the image center - 46 years ago we pulled the original neg and cropped it for a close-up of that plane. The overall Neutral Gray scheme was popular for Eighth and Fifteenth AF pathfinders.
Nice clear shot of P-38E and P-39D aircraft participating in the 1941 Carolina maneuvers. Note that none of the aircraft seem to have their full complement of guns installed, although the P-39 in the forefront seems to have wing guns that have been fired.