Lindsay Heimbach goes airborne while sledding down a hill on Mt. Lemmon December 27, 2008. (Photo by James Gregg/Arizona Daily Star)

A Harley Davidson biker is dressed as Santa Claus as he takes part in a charity ride in Zurich, Switzerland December 6, 2015. (Photo by Arnd Wiegmann/Reuters)

Jing Li (L) and her husband Ke Xu wear Tibetan traditional costumes as they pose for their wedding photos in front of Tibetan prayer flags at the Nianqing Tanggula mountain pass in the Tibet Autonomous Region, China November 18, 2015. Jing, 22, and her husband Ke Xu, 23, both from Shiyan in northwestern Hubei province live in Tibet for three year. The couple married last month. (Photo by Damir Sagolj/Reuters)

West Berliners crowd in front of the Berlin Wall as they watch East German border guards demolish a section of the wall on November 11, 1989. (Photo by Gerard Malie/AFP Photo)

Director Pawel Pawlikowski holds his Oscar for best foreign language film for “Ida”, with presenters Chiwetel Ejiofor (L) and Nicole Kidman during the 87th Academy Awards in Hollywood, California February 22, 2015. (Photo by Lucy Nicholson/Reuters)

Firefighters work to quell a fire on an alleged clandestine gasoline storage in the Ixtlahuaca community, Mexico on January 5, 2016. Looting broke out at dozens of stores in Mexico on Wednesday on the sidelines of protests against a steep gasoline price increase as authorities detained more than 200 people. (Photo by Mario Vazquez de la Torre/AFP Photo)

A Ukrainian serviceman who fought in Debaltseve is seen near Artemivsk February 19, 2015. Fighting raged in eastern Ukraine on Thursday despite European efforts to resurrect a still-born ceasefire, a day after pro-Russian separatists who spurned the truce forced thousands of government troops out of a strategic town. (Photo by Gleb Garanich/Reuters)

In this photo taken on Wednesday, February 17, 2016, a volunteer fighter with the Syrian Government forces sits atop a tank in the province of Raqqa, Syria. In recent weeks, Syrian government forces captured dozens of villages and towns across the country. (Photo by Alexander Kots/Komsomolskaya Pravda via AP Photo)