Soldiers from Japan's Ground Self Defense Force come ashore in amphibious assault vehicle as they train alongside U.S. Marines during the bilateral annual Iron Fist military training exercise in Camp Pendleton, California February 26, 2016. (Photo by Mike Blake/Reuters)

Two F-15E Strike Eagles wait to receive fuel from a KC-135R Stratotanker during exercise Red Flag 15-1 on their way to Nellis Air Force Base, Nev., Jauary 23, 2015. The F-15s are assigned to the 4th Fighter Wing. U.S. (Photo by Airman 1st Class Aaron J. Jenne/Reuters)

An armed forces members patrol during an operation against drug dealers in Vila Kennedy slum in Rio de Janeiro, March 7, 2018. (Photo by Pilar Olivares/Reuters)

Umbrellas are placed over the statute of the Beatles, during a photocall, on Liverpool's waterfront, in Liverpool, England, Wednesday, March 22, 2017. The city of Liverpool is getting set to celebrate the half-centenary of “Sgt. Pepper's Lonely Hearts Club Band”, one of the most influential albums by local heroes The Beatles. (Photo by Peter Byrne/PA Wire via AP Photo)

“The McDonnell Douglas KC-10 Extender is an air-to-air tanker aircraft in service with the United States Air Force derived from the civilian DC-10-30 airliner. The KC-10 was the second consecutive McDonnell Douglas transport aircraft to be selected by the US Air Force following the C-9 Nightingale. The similar KDC-10 is in service with the Royal Netherlands Air Force.”

Photo: A B-52G Stratofortress aircraft takes off with another B-52G close behind. Three cells of six B-52 and KC-10 Extender aircraft will takeoff seconds apart under combat conditions during the minimum interval takeoff exercise. The exercise is a part of an operational readiness inspection by the Strategic Air Command Inspector General Team. (Photo by USAF). 1998

Two dogs sent into outer space by the Soviet Union after their safe return to earth. They spent 22 days in orbit. (Photo by Central Press/Getty Images). 22nd March 1966

A Boeing 777-300 from Swiss International Airlines lands on a foggy morning at Zurich Airport, on Friday, October 13, 2017, in Zurich, Switzerland. The high humidity renders the air vortex visible. (Photo by Christian Merz/Keystone via AP Photo)

Enthusiasts gathered at Cad East in Snowdonia National Park, England to take pictures of F-15 Eagle fighters as they completed the Mach Loop, November 2017. (Photo by Caters News Agency)