Sure the guy at Normandy wasn't a Marine? They have a cross on the top of their dress covers...like to one on this catalog:
The dark ones have it as well.
As for the USAFA bubba, I would suspect it is to allow his friends/family find him in the crowd (or to find his service cap afterwards, they like to throw them up in the air after graduation then go scampering around afterward trying to find them. Another silly tradition).
Cheers! M2
By the way, the USAF doesn\'t have anything on the top of its service caps. All we have are clouds and lightning ("farts and darts") on the brim when we make field grade rank...
(freaking thing cost me $40!)
GO\'s get an even fancier version...
Note the USAF badge is not on the front of either.
Cheers! M2