Edited image
Both background and sky did not have much to offer. However I like this picture because it doubles as a pilots portrait with the sun hitting Warrens face. Everything is in focus and the sun is showing of the full prop disk. I processed the image in LR and used On1 Perfect Photo 9 to add dynamic contrast to the plane only. I used PS to fix the missing black paint on the fuselage. I tried to ad some blue to the sky to make it more interesting. Finally I worked in LR on the green, trying to match the intensity I remember.
RAW image