“Contrails (short for “condensation trails”) or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets or, if the air is cold enough, tiny ice crystals”. – Wikipedia

Photo: An airplane leaves a vapor trail as it flies in front of he moon on January 17, 2007 above Hanover, Germany. (Photo by Alexander Hassenstein/Getty Images)

In this Thursday, May 16, 2013 file photo, Finland's Krista Siegfrids, second right, kisses a dancer as she performs her song “Marry Me” during the second semifinal of the Eurovision Song Contest at the Malmo Arena in Malmo, Sweden. That was the first girl-on-girl kiss in the history of the annual competition. Previously, organizers had sought to prevent similar embraces citing the competition's status as a family event. (Photo by Alastair Grant/AP Photo)

A girl sticks out her tongue during snowfalls on a street in Hefei, Anhui province February 13, 2014. (Photo by Reuters/Stringer)

A girl sits on a pile of rubbish at landfill site on the outskirts of Sanaa, Yemen November 16, 2016. (Photo by Mohamed al-Sayaghi/Reuters)

A girl takes pictures after opening ceremony at Shanghai Disney Resort in Shanghai, China, June 16, 2016. (Photo by Aly Song/Reuters)

A Bangladeshi girl plays on a swing, in Dhaka, Bangladesh, December 27, 2016. (Photo by Mohammad Ponir Hossain/Reuters)

Two girls in cosplay dresses walk in the street in Beijing on March 27, 2017. (Photo by Fred Dufour/AFP Photo)