“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)

“The McDonnell Douglas KC-10 Extender is an air-to-air tanker aircraft in service with the United States Air Force derived from the civilian DC-10-30 airliner. The KC-10 was the second consecutive McDonnell Douglas transport aircraft to be selected by the US Air Force following the C-9 Nightingale. The similar KDC-10 is in service with the Royal Netherlands Air Force.”

Photo: A B-52G Stratofortress aircraft takes off with another B-52G close behind. Three cells of six B-52 and KC-10 Extender aircraft will takeoff seconds apart under combat conditions during the minimum interval takeoff exercise. The exercise is a part of an operational readiness inspection by the Strategic Air Command Inspector General Team. (Photo by USAF). 1998

The knitted sculpture “William Tell” by Patricia Waller sits in the “Broken Heroes” exhibition at the Deschler Gallery on April 26, 2012 in Berlin, Germany. The exhibition of hand-crocheted comic, puppet and cartoon figures shows icons of pop culture in various unfortunate states. (Photo by Adam Berry)

Video bloggers stream live broadcast of an event to celebrate the fourth birthday of the world's only giant panda triplets, Meng Meng, Shuai Shuai and Ku Ku, at Chimelong Safari Park in Guangzhou, China July 29, 2018. (Photo by Bobby Yip/Reuters)

An abandoned motorboat is seen on the bank of a bay near Krabozavodskoye settlement on the Island of Shikotan, one of four islands known as the Southern Kuriles in Russia and the Northern Territories in Japan, December 19, 2016. (Photo by Yuri Maltsev/Reuters)

High winds blow sand across the highway near the original north shore of Owens Lake, now miles from the nearest pool of water, on May 5, 2007 near Lone Pine, California. (Photo by David McNew/Getty Images)

Hot air balloons take part in the 38th International Balloon Festival of Chateau-d'oex, Switzerland, 23 January 2016. For nine days balloonists from 15 countries take part in the ballooning event in the Swiss mountain resort famous for ideal flight conditions due to an exceptional microclimate. The festival takes place from 23 to 31 January. (Photo by Cyril Zingaro/EPA)

A U.S. Air Force B-1B Lancer bomber sits on the runway at Anderson Air Force Base, Guam July 18, 2017. (Photo by Airman 1st Class Christopher Quail/Reuters/U.S. Air Force)