US Air Force Security Forces Phoenix Raven Sticker. This rounded circle has the emblem of the Phoenix Raven program ran by Security Forces and offering Global Protection.  You can read more about the Phoenix Raven course and how to become a Phoenix Raven on their website.

What Is A Phoenix Raven?

"Air Mobility Command's Phoenix Raven program, implemented in 1997, consists of teams of specially trained security forces personnel dedicated to providing security for Air Mobility Command aircraft transiting high terrorist and criminal threat areas." - http://www.amc.af.mil/