TRAVIS AIR FORCE BASE, Calif. -- Senior Airman Christopher Whalen, 349th Security Forces Squadron, defends the landing zone as a California Army National Guard UH-60 Black Hawk helicopter lands for a simulated blood transferJune 6, 2015 at Travis Air Force Base, California.More than 40 defenders took part in a various expeditionary combat skills training scenarios during the Air Force Specialty Code weekend. (U.S. Air Force photo/ Staff Sgt. Christopher Carranza)