U.S. Secretary of Defense Dr. Mark T. Esper observes an in-air refueling of an E-4B Advanced Airborne Command Post by a KC-10 Extended Aerial Refueling Tanker over the Pacific Ocean, Aug. 2, 2019. The 60th Air Mobility Wing from Travis Air Force Base, California, supported the refueling. (DoD video by Lisa Ferdinando)
