People at a Czech Stop look at a cloud of smoke rising from the explosion in West, Texas, April 17, 2013. (Photo by Andy Bartee via Dallas Morning News/MCT)

Hot air balloons rise over Innes Common Park during a dawn lift on March 29, 2012 in Hamilton, New Zealand. Each Autumn over 30 hot air balloons grace the sky as part of the Balloons Over Waikato Festival. (Photo by Sandra Mu/Getty Images)

A tornado builds and travels southwest causing damage near Dean Rd. and 82nd Avenue in Hutchinson, Kan. on Monday, July 13, 2015. (Photo by Sandra J. Milburn/The Hutchinson News via AP Photo)

Prospective flight attendants listen to their instructor during an etiquette training course at Indigo Airlines' Ifly training centre in Gurgaon on the outskirts of New Delhi November 18, 2014. (Photo by Adnan Abidi/Reuters)

A young prince, dressed ready for the coronation of new Emir of Kano Muhamadu Sanusi II, is pictured in Kano, Kano State, February 7, 2015. (Photo by Afolabi Sotunde/Reuters)

A Ukrainian serviceman wearing a new year's hat waves at his comrades while standing beside his tank near Debaltseve, eastern Ukraine, February 8, 2015. (Photo by Gleb Garanich/Reuters)

A woman takes a selfie in front of a Lunar New Year display featuring sheep at a shopping mall in Hong Kong, February 13, 2015. (Photo by Bobby Yip/Reuters)

Arctic wolves in their new enclosure in the wildlife park in Hanau, Germany, 10 February 2015. The pack is one of the park's main attractions, which specializes in local and European breeds. (Photo by Boris Roessler/EPA)