A prototype battery-powered plane, called Greased Lightning or GL-10 is pictured flying at NASA's Langley Research Center in this undated handout photo obtained by Reuters May 1, 2015. The plane, which has 10 engines and can take off like a helicopter and fly efficiently like an aircraft, is currently in the design and testing phase. (Photo by Reuters/NASA)

An officer wipes sweat off the face of a Chinese People's Liberation Army (PLA) honor guard soldier as they rehearse for a welcoming ceremony for New Zealand's Governor-General Sir Jerry Mateparae at the Great Hall of the People in Beijing, Tuesday, July 21, 2015. (Photo by Mark Schiefelbein/AP Photo)

Performers of circus company Circa perform during a photocall for the Edinburgh Festival Fringe on Calton Hill on August 1, 2017 in Edinburgh, United Kingdom. (Photo by Murdo MacLeod/The Guardian)

The entire cast perform during a production media call for Singin' In The Rain at Her Majesty's Theatre on May 12, 2016 in Melbourne, Australia. (Photo by Robert Cianflone/Getty Images)

Russian artist Maria Gazanova (L) works on her "The Alive Painting" art work during the Art Krasnoyarsk annual festival in Siberian city of Krasnoyarsk, Russia November 4, 2015. (Photo by Ilya Naymushin/Reuters)

A commuter gestures to Boris Johnson as he rides across Vauxhall Bridge in London, England on November 19, 2015. The London mayor was opening a cycle superhighway. (Photo by John Stillwell/PA Wire)

Model feebee poses as part of art installation “Dazzle room” made by artist Shigeki Matsuyama at Room 32 fashion and design exhibition in Tokyo, Friday, February 19, 2016. Matsuyama's installation features a strong contrast of black and white, which he learned from dazzle camouflage used mainly in World War I, in Tokyo, Friday, Feb. 19, 2016. (Photo by Shuji Kajiyama/AP Photo)

A female soldier from the honour guards prepares for a welcoming ceremony for Uruguay's President Tabare Vazquez at the Great Hall of the People in Beijing, China, October 18, 2016. (Photo by Jason Lee/Reuters)