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)

A reveller takes part in the Gay Pride Parade in San Salvador, on June 24, 2017. (Photo by Marvin Recinos/AFP Photo)

The Peugeot of Sebastien Loeb of France is seen turned over next to a helicopter during the eighth stage in the Dakar Rally 2016 near Belen, Argentina, January 11, 2016. (Photo by Andre Lavadinho/Reuters/World-ASO)

U.S. Army helicopters providing support for U.S. ground troops fly into a staging area fifty miles northeast of Saigon, Vietnam, August 28, 1966. Helicopter fuel is stored in the large rubber tanks, foreground. (Photo by Henri Huet/AP Photo)

A female participant of the Bela Negara – “defend the nation” – programme applies camouflage face paint on another participant's face at a training centre in Rumpin, Bogor, West Java, Indonesia June 2, 2016. (Photo by Darren Whiteside/Reuters)

Commonwealth dance group on the right track with Virgin Trains – Photo call at Glasgow Central Station. (Photo by Daily Record)

Labrador puppies “Hoey” (L) and “Hatton”, named in honor of September 11, 2001 attack victims Patrick Hoey and Lenny Hatton who died in the World Trade Center, are pictured on the grounds of the Pentagon near Washington, June 28, 2011. (Photo by Jason Reed/Reuters)

Ultra- trailers compete at sunrise on September 2, 2017 in Courmayeur, Italy, during the 15 th edition of the Mount Blanc Ultra Trail (UTMB), a 170 km race around the Mont Blanc crossing France, Italy and Switzerland. The 15 th Ultra- Trail du Mont- Blanc (UTMB) is a mountain ultramarathon with numerous passages in high altitude (>2500 m) and in difficult weather conditions (night, wind, cold, rain or snow). (Photo by Jeff Pachoud/AFP Photo)