Two Czech Gripen fighter planes demonstrate a flight interception of a Belgian air force transport plane over the Czech Republic, as part of NATO drills on September 12, 2018. (Photo by Francois Lenoir/Reuters)

A first white-handed gibbon infant born at the Skopje Zoo is seen with his mother in Skopje, North Macedonia on May 9, 2019. (Photo by Ognen Teofilovski/Reuters)

A man passes by a wall with graffiti in Beirut, Lebanon, on May 29, 2019. (Photo by Bilal Jawich/Xinhua News Agency/Alamy Live News)

Demonstrators protest against bullfighting in front of the City Hall a day before of the famous San Fermin festival, in Pamplona, northern Spain, Friday, July 5, 2019. The festival will begin on July 6 with the “txupinazo” opening ceremony, with people participating in bull runs, music and dance, through the old city. (Photo by Alvaro Barrientos/AP Photo)

Socialite Kathy Hilton attends the Prudential Financial Grand Prix Hamptons Classic Horse Show August 31, 2003 in Bridgehampton, New York.

A deer forages for food in the early morning sun as cooler temperatures bring on the autumn season at Dunham Massey on on October 11, 2010 in Lymm, England. Shortening daylight hours and cooler weather brings on the rutting season for Red and Fallow deer herds and Autumn foliage colours across Britain. (Photo by Christopher Furlong/Getty Images)

“NASA's Pathfinder, Pathfinder Plus, Centurion and Helios Prototype were an evolutionary series of solar- and fuel-cell-system-powered unmanned aerial vehicles. AeroVironment, Inc. developed the vehicles under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program. They were built to develop the technologies that would allow long-term, high-altitude aircraft to serve as “atmospheric satellites”, to perform atmospheric research tasks as well as serve as communications platforms”. – Wikipedia

Photo: The solar-electric Helios Prototype flying wing is flies over the Hawaiian islands of Niihau and Lehua during the first solar-powered test flight July 14, 2001 from the U.S. Navy's Pacific Missile Range Facility on Kauai, HI. The 18-hour flight was a functional checkout of the aircraft's systems and performance in preparation for an attempt to reach sustained flight at 100,000 feet altitude later in the summer. (Photo Courtesy of NASA/Getty Images)