“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)

David Sharp, an engineer with Lockheed Martin, displays the “Samurai Flyer”, an aviation design inspired by the maple seed, during the Association for Unmanned Vehicle Systems International Conference August 16, 2011 in Washington, DC. Lockheed Martin unveiled the new design and demonstrated vertical takeoff and landing, stable hover, and on-board video streaming of the aircraft during their demonstration. (Photo by Win McNamee/Getty Images)

A Felix Airways plane is seen after it was destroyed by an airstrike at the international airport of Yemen's capital Sanaa, April 29, 2015. Jets from a Saudi-led alliance destroyed the runway of Yemen's Sanaa airport on Tuesday to prevent an Iranian plane from landing there, Saudi Arabia said, as fighting across the country killed at least 30 people. Airport officials said the strikes set a civilian aircraft operated by Yemeni Felix Airways ablaze. (Photo by Khaled Abdullah/Reuters)

The public get the first view at the opening of the new miniature model Knuffingen Aiport at Miniatur Wunderland on the airport's opening day on May 4, 2011 in Hamburg, Germany. Miniatur Wunderland is the world's largest model railroad landscape, and the model airport, also the world’s largest, goes into operation following 6 years of development and construction and an investment of EUR 3.5 million. The airport is a reproduction of Hamburg’s international airport and includes 40 aircraft that take off and land and 90 vehicles that autonomously move around the runways on May 4, 2011 in Hamburg, Germany. (Photo by Stuart Franklin/Getty Images)

This image taken from video provided by TVBS shows a commercial airplane clipping an elevated roadway just before it careened into a river in Taipei, Taiwan, Wednesday, February 4, 2015. The ATR-72 prop-jet aircraft had 58 people aboard. (Photo by AP Photo/TVBS)

A five-month-old female slender loris waits to be given her first health check by the veterinary team at London Zoo on July 21, 2011 in London, England. Two female baby slender lorises, who are yet to be named, were given health checks, their s*x determined and micro-chipped. Slender Loris is the common name for the strepsirrhine primates who are nocturnal and originate from India, Sri Lanka, and southeast Asia. London Zoo supports conservation of lorises in Sri Lanka, where populations are thought to be under threat from deforestation. (Photo by Christopher Furlong/Getty Images)

This photo taken on January 28, 2018 shows participants taking part in games on stage during the “&Proud” LGBT festival in Yangon. Races, games, music and fun were just some of the highlights of the “&Proud” LGBT festival, which took place in a Yangon public park for the first time at the weekend in a country where same-s*x relations are still officially illegal. (Photo by Ye Aung Thu/AFP Photo)

Ethiopian Airlines female pilots prepare the plane before takeoff at Bole international airport in the capital Addis Ababa, November 19, 2015. Ethiopia Airlines on Thursday, dispatched its first ever all-female operated flight. Every aspect of the journey was handled by women, from the ground crew, aircraft maintenance to traffic controllers. Gualu and her co-pilot were charged with flying the crew and passengers to Bangkok, Thailand. (Photo by Tiksa Negeri/Reuters)