Aircrew and maintenance Airmen assigned to the 22nd Air Refueling Wing conduct preflight checks before a training sortie, June 3, 2016, at McConnell Air Force Base, Kan. Before every mission, Airmen work together to ensure the aircraft is air worthy. (U.S. Air Force photo/Staff Sgt. Rachel Waller)

A KC-135 Stratotanker assigned to 22nd Air Refueling Wing approaches another KC-135 for aerial refueling, June 3, 2016, over Kansas. Some of the 59-year-old aircraft have been modified to receive fuel while in-flight. (U.S. Air Force photo/Staff Sgt. Rachel Waller)

A KC-135 Stratotanker offloads fuel to another KC-135, June 3, 2016, over Kansas. Both aircraft are assigned to McConnell Air Force Base, Kan., and train together regularly. (U.S. Air Force photo/Staff Sgt. Rachel Waller)

A KC-135 Stratotanker assigned to McConnell Air Force Base, Kan., receives fuel from another KC-135 during a training sortie, June 3, 2016, over Kansas. Aircrews regularly train together to ensure they’re proficient when they perform aerial refueling. (U.S. Air Force photo/Staff Sgt. Rachel Waller)

A KC-135 Stratotanker detaches from a KC-135 boom after receiving fuel, June 3, 2016, over Kansas. Not only can certain KC-135s take on fuel, but they provide refueling support to Department of Defense and allied aircraft thereby increasing their reach. (U.S. Air Force photo/Staff Sgt. Rachel Waller)