Wolfgang (L), member of World War One historical association “Darstellungsgruppe Suddeutsches Militar 1870-1918” (DSM 18), from Munich, Germany, and Florent, member of French association “Le Poilu de la Marne”, dressed in vintage army uniforms, visit the Bezonvaux bunker in the national forest of Verdun, eastern France, March 29, 2014. Members of French and German historical associations, who gather annually, together visited the battlefield of Verdun in France, the site of a bloody World War One battle that dragged on for around 10 months in 1916, claiming hundreds of thousands of lives and destroying many villages. (Photo by Charles Platiau/Reuters)

“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)

Members of the Women's Fire Brigade with their Chief Officer, March 1916. (Photo by Topical Press Agency)

A staff member at the Rising Sun Anger Release Bar suits up in protective gear August 8, 2006 in Nanjing of Jiangsu Province, China. (Photo by China Photos/Getty Images)

Girls Aloud: Nicola Roberts, Kimberley Walsh, Sarah Harding and Cheryl Cole at Kimberley Walsh's birthday party hosted by Damian Darkko at Mint Nightclub in London, Britain on November 25, 2006. The Girls Aloud star Sarah Harding has died at the age of 39, her mother has said in a post on Instagram. Issue date: Sunday September 5, 2021. (Photo by Rex Features/Shutterstock)

Indian girl, Amrita Bannerjee, gets dressed as the Goddess Durga, during Kumari Puja ritual as part of the Durga Puja festival at Shidaspur village, far north of Kolkata, India, 30 September 2025. During the Kumari Puja, devotees worship a girl aged between six and twelve, symbolizing the Kanya Kumari (virgin) form of the Goddess Durga Devi. Hindu devotees believe that Kanya is a living embodiment of the goddess Durga. (Photo by Piyal Adhikary/EPA)

Homeless people queue to get free hot food organized by social services during frost winter day in-Kiev on December 18, 2012. Nineteen people died of exposure in Ukraine in the last 24 hours amid temperatures of minus 20 degrees Celsius (minus 4 degrees Fahrenheit), bringing the toll this month to 37, the health ministry said Tuesday. (Photo by Sergei Supinsky/AFP Photo)

In this Monday, June 29, 2020 a man wearing a face mask to protect against coronavirus, walks past a hair product billboard on the street in Soweto, Johannesburg, South Africa. Africa now has more than a half-million confirmed coronavirus cases as the continent-wide total is now over 508,000 after South Africa recorded another day of more than 10,000 confirmed cases as a new global hot spot. (Photo by Themba Hadebe/AP Photo/File)