A U.S. Air Force crew chief marshals a C-17 aircraft assigned to the 97th Air Mobility Wing, Altus Air Force Base, Okla., on the Nellis flight line after the crew participated in the Mobility Air Forces Exercise May 23, 2012 over the Nevada Test and Training Range. More than 20 C-17s assembled in aerial formations over the NTTR to conduct air and ground operations as part of the Air Force Weapons School Mobility Air Forces Exercise.