I just noticed this on the skin I'm working on, and checked against a number of other skins, both custom and default. The ingame sunlight appears to be so intense it burns the skin right off the tip of the pilot's nose and sunward cheek. The skin tone color disappears into a white patch, as if it's made of highly specular substance.
I tried making a DUDE1_S.bmp but it didn't seem to make a difference.
I also tried reverting to a pure black specularity file, but it doesn't make any difference. So far I've noticed it on the P-38, Spit IX, F4U, and P-47 pilots. P-51 pilot wasn't affected, neither was the N1K2 or Yak 9U.