“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)

An officer reviews members of the honor guard as they line up before a welcoming ceremony for visiting Mozambique's President Filipe Jacinto Nyusi at the Great Hall of the People in Beijing, Wednesday, May 18, 2016. (Photo by Mark Schiefelbein/AP Photo)

People take part in fake festival called “La Boum” organized by an anonymous group of people on Facebook for an April 1 joke at the Bois de la Cambre, in Brussels, Belgium, 01 April 2021. An anonymous group created a Facebook event called “La Boum”, touting an alleged festival to take place with famous DJs as headliners. Thousands of people on social media had shown interest to take part in the gathering, while police have advised that no authorization has been given for a music event. (Photo by Stephanie Lecocq/EPA/EFE)

A woman counts her money as she sells flowers ahead of International Women's Day in central Kiev, Ukraine on March 7, 2019. (Photo by Gleb Garanich/Reuters)

A staff member sets up a ROBOTLEO robot at the Global Mobile Internet Conference (GMIC) 2017 in Beijing, China April 28, 2017. (Photo by Jason Lee/Reuters)

Festival goers dance during Glastonbury Festival at Worthy Farm, near Pilton, Somerset, Britain, 23 June 2017. The outdoor festival runs from 21 to 25 June. (Photo by Nigel Roddis/EPA)

A looter smiles as she runs away from a member of the South African Police Services (SAPS) inside the Lotsoho Mall in Katlehong township, East of Johannesburg, on July 12, 2021. Several shops are damaged and cars burnt in Johannesburg, following a night of violence. Police are on the scene trying to control further protests. It is unclear if this is linked to sporadic protests following the incarceration of former president Jacob Zuma. (Photo by Phill Magakoe/AFP Photo)

China's Shang Chunsong prepares to compete in the uneven bars event of the women's individual all-around final artistic gymnastics competition at the Namdong Gymnasium Club during the 17th Asian Games in Incheon, in this September 23, 2014 file photo. (Photo by Kim Hong-Ji/Reuters)