Conference Hall Defense Secretary Jim Mattis speaks during the Air Force Association Air, Space and Cyber Conference at National Harbor, Md., Sept. 20, 2017. DoD photo by U.S. Air Force Tech. Sgt. Brigitte N. Brantley SHARE IMAGE: Download Image: Full Size (1.03 MB) Photo By: Brigitte N. Brantley VIRIN: 170920-D-GO396-0176L.JPG Photo Gallery