Secretary of Defense Chuck Hagel waves goodbye as he boards an aircraft after presiding over a U.S. Transportation Command change of command ceremony at Scott Air Force Base, Ill., May 5, 2014. Hagel welcomed U.S. Air Force Gen. Paul J. Selva, the incoming commander of USTRANSCOM, to the post during the ceremony and presided over retirement proceedings for outgoing commander Gen. William M. Fraser III, who retired after 40 years of service.