Russian President Vladimir Putin (C) and Defence Minister Sergei Shoigu (back) attend a reception to honour graduates of military academies at the Kremlin in Moscow, Russia, June 28, 2016. (Photo by Alexei Druzhinin/Reuters/Sputnik/Kremlin)

Labourers pour molten iron into a container at a foundry in Xiangfan, Hubei province in this July 2, 2010 file photo. Iron ore is enjoying its biggest rally in years, outpacing copper and oil so far in 2016, but still weak forward prices show it may be tough to stretch the bullish outlook. Improving steel prices in top market China are helping fuel iron ore's climb as producers gear up for a seasonal uptick in demand. Yet there is no shortage of doubters who see gains in the bulk commodity as fleeting given a large glut and challenges for China's economy. (Photo by Reuters/Stringer)

Children of Indian laborers play on make-shift swings in Amritsar, India, May 12, 2015. (Photo by Narinder Nanu/AFP Photo)

A woman rides a donkey during a donkey race in Roum village, Jizeen countryside, southern Lebanon, August 9, 2015. (Photo by Ali Hashisho/Reuters)

Visitors review their cell phone photos of an installation called “Plexus A1” by artist Gabriel Dawe, one of nine large-scale art installations displayed at the “Wonders” exhibit at the Renwick Art Gallery in Washington, DC, Wednesday, January 13, 2016. Built in the 1860s, the Renwick was the first American building to be designed specifically as an art museum; it recently reopened after a two year renovation. (Photo by Jim Lo Scalzo/EPA)

Visitors looks at the flying car Pegasus 1, built by French entrepreneur Jerome Dauffy at Paris Air Show, in Le Bourget, east of Paris, France, Tuesday, June 20, 2017. Aviation professionals and spectators are expected at this week's Paris Air Show, coming in, in a thousands from around the world to make business deals. (Photo by Michel Euler/AP Photo)

An Army Sikorsky VH-34s Choctaw helicopter once used to transport President Dwight D. Eisenhower sits in a field at the 309th Aerospace Maintenance and Regeneration Group boneyard Thursday, May 14, 2015 at Davis-Monthan Air Force Base in Tucson, Ariz. President Eisenhower became the first chief executive to be transported by helicopter. Presidents Eisenhower and John F. Kennedy were transported in VH-34 helicopters and VH-34's served as “Army One” from 1958 through 1963. (Photo by Matt York/AP Photo)