Fishermen collect their catch from a net at Dojran Lake, Macedonia, January 4, 2017. Fish from the lake is a traditional food for locals for orthodox Christmas eve, which falls on January 6. The lake faced sustainability issues during the 1990s due to drought and excessive use of its water but has since recovered after measures were taken to replenish and sustain water levels, according to local media. Dojran Lake is one of the three natural lakes in Macedonia, and also the warmest. It is said it is also the richest lake in fish in Europe. (Photo by Ognen Teofilovski/Reuters)

A walker has left a handprint on a snow- covered tree trunk on Grosser Feldberg mountain in the Taunus mountain range, Germany, 16 January 2017. (Photo by Frank Rumpenhorst/DPA)

A long time exposure shows a Igloo at the “Igloo village” (Iglu Dorf) in front of the famous Matterhorn mountain in Zermatt, Switzerland, late 28 January 2016. The hotel-igloo village made of snow and ice at 2'815 meters about sea level with a bar, a restaurant, bedrooms and wellness are celebrating their 20th anniversary. For this occasion the hosts built the largest classic igloo with a diameter of 13 meters and a ceiling hight of 11 meters in front of Matterhorn in Zermatt, and they will attempt the world record for this Igloo. (Photo by Jean-Christophe Bott/EPA)

“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

An Aerial view Admiralty Arch at the top of The Mall on July 26, 2011 in London, England. (Photo by Tom Shaw/Getty Images)

Air conditioners, more than 500 in total, hang on the wall of an office building on August 15, 2011 in Fuzhou, Fujiang Province of China. This 25-story office building was built with no central air conditioner system, each office has it own individual unit installed on the exterior creating this wall of air conditioners. (Photo by ChinaFotoPress/Getty Images)

A Saudi soldier fires a mortar towards Houthi movement position, at the Saudi border with Yemen April 21, 2015. (Photo by Reuters/Stringer)

The Royal Air Force aerobatic team, the Red Arrows, perform during The Royal International Air Tattoo at the RAF in Fairford July 11, 2014. (Photo by Stefan Wermuth/Reuters)