Tank crew standing in front of M-4 tank, Ft. Knox, Kentucky, June, 1942. (Alfred Palmer/OWI/LOC)

A Lockheed Super Constellation “Super Connie” lands during the Air14 airshow at the airport in Payerne August 30, 2014. The Swiss Air Force celebrates their 100th anniversary with the biggest airshow in Europe this year. (Photo by Ruben Sprich/Reuters)

Culinary Specialist 2nd Class Jaqueline Rodriguez subdues a simulated suspect after being sprayed with oleoresin capsicum (OC) spray during security training aboard the amphibious dock landing ship USS Comstock (LSD 45). (U.S. Navy photo by Mass Communication Specialist 2nd Class Joseph M. Buliavac/Released). May 10, 2011

Aerial acrobat Schindler, notorious for his foolhardy stunts, practising one of his tricks listing out of the vertical, from a Klemp plane piloted by Richard Perlia. (Photo by General Photographic Agency/Getty Images). Circa 1927

Željava Air Base, situated on the border between Croatia and Bosnia and Herzegovina under Plješevica Mountain, near the city of Bihać, Bosnia, was the largest underground airport and military air base in the former Yugoslavia, and one of the largest in Europe. (Photo by Thomas Windisch/Exclusivepix Media)

A passenger plane, with a full Harvest moon seen behind, makes its final landing approach towards Heathrow Airport in London, Britain, October 5, 2017. (Photo by Toby Melville/Reuters)

In this Wednesday, July 13, 2016, handout image provided by Solar Impulse, the Solar Impulse 2 flying over the pyramids, Egypt Cairo. The experimental solar-powered airplane has arrived in Egypt as part of its global voyage. (Photo by Jean Revillard, Rezo via the AP Photo)

Pedestrians look at “doll” model Lulu Hashimoto standing on the street during a photo opportunity for Reuters in Tokyo, Japan August 23, 2017. (Photo by Kim Kyung-Hoon/Reuters)