A 314th Air Refueling Squadron KC-135 Stratotanker refuels a 22nd Airlift Squadron C-5 Galaxy Dec. 21, 2016, over the Sierra Nevada Mountains, California. The 314th ARS is located at Beale Air Force Base and the 22nd Airlift squadron is from Travis Air Force Base. The KC-135 has been in service since 1956 and can refuel a variety of aircraft. (U.S Air Force photo/Airman Tristan D. Viglianco)

A KC-135 Stratotanker from Beale Air Force Base, California, refuels a KC-10 Extender, from Travis Air Force Base, California, December 22, 2016. The pilots and crew on board the KC-135 are with the 314th Aerial Refueling Squadron, Beale Air Force Base, California, and the pilots and crew aboard the KC-10 are with the 60th Formal Training Unit, Travis Air Force Base, California. (U.S. Air Force photo/ Staff Sgt. Bobby Cummings)

A KC-135 Stratotanker with the 314th Air Refueling Squadron, Beale Air Force Base, California, soars above the Sierra Nevada Mountains, December 22, 2016. KC-135s have played a vital role in the United States Air Forces aerial refueling capabilities since the 1950s. (U.S. Air Force photo/ Staff Sgt. Bobby Cummings)

Lt. Col. Jenni Pfafman and Maj. Nathan Walker, 314th Air Refueling Squadron KC-135 Stratotanker pilots, review a preflight checklist Dec. 21, 2016 at Beale Air Force Base, California. Beale recently saw the arrival of the remainder of the 940th Air Refueling Wing’s KC-135s. (U.S Air Force photo/Airman Tristan D. Viglianco)

Tech. Sgt. Richard Costaflis, a 314th Air Refueling Squadron boom operator from Beale Air Force Base refuels a 22nd Airlift Squadron C-5 Galaxy from Travis Air Force Base, Dec. 21, 2016, over the Sierra Nevada Mountains, California. Boom operators are responsible for in-flight refueling various aircraft. (U.S Air Force photo/Airman Tristan D. Viglianco)