Sukhoi Su-30SM jet fighters of the Russkiye Vityazi (Russian Knights) aerobatic team perform during a demonstration flight in Krasnoyarsk, Russia October 6, 2018. (Photo by Ilya Naymushin/Reuters)

A tourist poses for a souvenir snap in front of autumn foliage in Pitlochry, Scotland, Britain on September 28, 2018. (Photo by Russell Cheyne/Reuters)

Soldiers on exercise in Kenya. The image, by Sergeant Dek Traylor, is among the section winners in the UK Army Photographic Competition 2018. (Photo by Sergeant Dek Traylor/PA Wire Press Association)

An Emirati child plays with an airplane model near the venue of the Mazayin Dhafra Camel Festival, on December 20, 2012 near the city of Madinat Zayed, 150 kms west of Abu Dhabi. The festival, which attracts participants from around the Gulf region, includes a camel beauty contest, a display of UAE handcrafts and other activities aimed at promoting the country's folklore. (Photo by Karim Sahib/AFP Photo)

A general view shows the part of the skyline of Dubai covered in an early morning fog on October 5, 2015. (Photo by Rene Slama/AFP Photo)

Valery Bystritskii, 10, gets a fellow student into a lock at Bunny's Gym in July 2015 in Winchester, Tennessee. (Photo by Mike Saliba/Barcroft USA)

A visitor takes in a view of the downtown district from Twin Peaks on Friday, January 9, 2015, in San Francisco. (Photo by Marcio Jose Sanchez/AP Photo)

Snow covers roofs, streets and the Charles River following a winter blizzard in Boston, Massachusetts January 28, 2015. A powerful blizzard struck Boston and surrounding New England on Tuesday, leaving some 4.5 million people grappling with as much as three feet of snow and coastal flooding. (Photo by Brian Snyder/Reuters)