Early war german air recognition?

Hi all,

This one goes out to all those treadheads out there, maybe one of you can help me out. I was looking at some pictures of early war (circa 1940) german armor, and some of the tanks had solid white bands painted on their tops. It seems to be for air recognition, but I only knew of swasticas or national flags used for that, never solid white bands...the pictures don't have any captions or explanations, so i don't know if these tanks belong to a particular unit that had a special paint job. Does anybody know of any panzer units that would have used these bands on their armor?

Thanks in advance