Air Force One casts its shadow over homes as it comes in to land in Allentown, Pennsylania with U.S. President George W. Bush aboard in this October 1, 2004 file photo. (Photo by Jason Reed/Reuters)

Austrian artist Erwin Wurm (R) stands next to an extra of his participation sculpture “Hose lueften, Haende hoch” (air out pants, hands high) at the garden of the Staedel Museum, in Frankfurt am Main, Germany, 06 May 2014. The series “Wurm: One Minute Sculptures” include painted or written instructions tell the person what they have to do and where for 60 seconds. The exhibition runs from 07 May to 13 July. (Photo by Arne Dedert/EPA)

An Afghan child practices walking with his new prosthesis at the International Committee of the Red Cross (ICRC), orthopedic center on September 10, 2011 in Kabul, Afghanistan. After more than 30 years of war and a decade since the 9/11 attacks in the United States, thousands of Afghans, both military and civilian, continue to pay a heavy price from the conflict. The ICRC center makes prosthetics for amputees and helps them, as well as Afghans with spinal injuries and children with congenital birth defects, to learn to walk. (Photo by John Moore/Getty Images)

A 10 week old stuffed Tiger cub and a Tortoise are displayed in a cabinet at an “Endangered Species” exhibition at London Zoo on September 12, 2011 in London, England. The exhibition is organised by “Operation Charm”, a Metropolitan Police partnership aimed at tackling the illegal trade in endangered wildlife and runs for one month at London Zoo. Items include the tooth of a sperm whale, Ivory carvings, and a stuffed Tiger. (Photo by Dan Kitwood/Getty Images)

A woman react inside a cloud of paint powder during the holi one colour Festival held in the city of Cape Town, South Africa, Saturday, March 2, 2013. Thousands of people are taking part in the festival by throwing coloured paint powder at each other to express freedom and the colour of everyday life. (Photo by Schalk van Zuydam/AP Photo)

Brazilian gymnast Jade Barbosa is seen during a training session at the new Brazilian Artistic Gymnastics Center in Rio de Janeiro January 16, 2015. The Artistic Gymnastics Center is where gymnasts are preparing for the 2016 Olympics. (Photo by Sergio Moraes/Reuters)