Senior Airman Christopher Martinez, 8th Expeditionary Air Mobility Squadron crew chief, purges a tank of liquid oxygen as he recharges a C-17 Globemaster III at Al Udeid Air Base, Qatar, Sept. 3, 2016. Martinez joined the Air Force in November 2013 to follow his father’s footsteps as a crew chief and later on cross-trained to the electrical field. Air Force photo by Senior Airman Janelle Patiño