Members of the U.S. Army 173rd Airborne Brigade stand at attention as a Ukrainian folk dance group performs at the opening ceremony of the “Rapid Trident” NATO military exercises on September 15, 2014 near Yavorov, Ukraine. The two-week exercises include participating units from a variety of NATO and NATO-associate countries as well as Ukrainian troops. Meanwhile fighting between pro-Russian separatists and Ukrainian armed foces has flared again in eastern Ukraine in a battle for the control of Donetsk airport despite the tenuous ceasefire. (Photo by Sean Gallup/Getty Images)

This April 9, 2016 photo provided by Bertrand Piccard via Global Newsroom shows Piccard taking a selfie on board Solar Impulse 2 during a test flight over the Pacific Ocean. The solar-powered airplane on an around-the-world journey had traveled 80 percent of the way from Hawaii to California by Saturday, April 23. The aircraft's destination on this leg of the journey is Mountain View, Calif., at the southern end of San Francisco Bay. (Photo by Bertrand Piccard/Global Newsroom via AP Photo)

A man salts a downtown sidewalk in Washington, Thursday, March 5, 2015, as snow begins to fall. The U.S. federal government said its offices in the Washington area will be closed Thursday because of a new round of winter weather expected in the region. The Office of Personnel Management said non-emergency personnel in and around Washington were granted excused absences for the day. Emergency employees and telework-ready employees were expected to work. (AP Photo/Andrew Harnik)

Two stags fight in a wildlife park in Aurach near Kitzbuehel, in the Austrian province of Tyrol. (Photo by Kerstin Joensson/Associated Press)

French army deminers secure a helicopter in a hangar at the Gao airport, on February 9, 2013. Two Malian soldiers and four civilians have already been killed by landmines, and French troops are still fighting off what Paris called “residual jihadists” in reclaimed territory. (Photo by Pascal Guyot/AFP Photo via The Atlantic)

Rutgers Scarlet Knights cheerleaders perform during a game against the Connecticut Huskies at High Point Solutions Stadium on October 6, 2012 in Piscataway, New Jersey. Rutgers defeated Connecticut 19-3. (Photo by Rich Schultz)