Afghan air force 2nd Lt. Niloofar Rhmani walks the flight line at Shindand Air Base, Afghanistan, prior to her graduation from undergraduate pilot training, on May 13, 2013. Rhmani made history on May 14, when she became the first female to successfully complete undergraduate pilot training and earn the status of pilot in more than 30 years. She will continue her service as she joins the Kabul Air Wing as a Cessna 208 pilot. (Photo by Senior Airman Scott Saldukas/USAF)

These are the stomach-churning pictures of the swing at the end of the world – a rickety wooden swing hanging over a precipice 2,660 metres above sea level – and not a seatbelt in sight. (Photo by Caters News)

A biker passes by a pair of mailboxes in the Capitol Hill neighborhood November 6, 2012 in Denver, Colorado. Colorado is considered by most experts to be one of the key battleground state in this year's presidential election. (Photo by Marc Piscotty/AFP Photo)

In this April 2, 2016 photo, dusty sculptures made of cast-off baby dolls sit in an open-air museum and art workshop off a trash-strewn street cutting through some of the poorest neighborhoods in Port-au-Prince, Haiti. They were created by Haitian artists called Atis Rezistans who have become celebrated in the international art world by creating sculptures out of scrapped car parts, old wood, discarded toys and even human skulls found scattered outside crumbling mausoleums. (Photo by David McFadden/AP Photo)

Passengers brave the strong winds as they wait for a bus, in Hong Kong, Monday, September 15, 2014. The Hong Kong Observatory issued the number 8 southeast storm signal, as Typhoon Kalmaegi edges closer to Hong Kong. (Photo by Kin Cheung/AP Photo)

A hot air balloon floats over farm fields south of Washington, Ill., as the sun slips behind clouds on the autumn afternoon of Wednesday, September 24, 2014. (Photo by Ron Johnson/AP Photo/Peoria Journal Star)

Alex Plunkett, left, and Sean Hart, both of Arlington, Va., join hundreds participating in the annual International Pillow Fight Day on April 5. Massive pillow fights broke out on the Mall in Washington and in cities around the world. (Photo by Marvin Joseph/The Washington Post)