U.S. Air Force Senior Airman John McLaughlin, an aerospace ground equipment journeyman assigned to the 509th Maintenance Squadron, replaces pins on a MD-1 towbar May 31, 2012, at Whiteman Air Force Base, Mo. These airmen were responsible for maintaining the equipment that supplies electricity, hydraulic pressure and air pressure, as planes receive maintenance and prepare for flight. (U.S. Air Force photo by Senior Airman Nick Wilson/Released)