U.S. first lady Melania Trump steps out of her motorcade vehicle as she departs Washington for a tour of several African countries from Joint Base Andrews, Maryland, U.S., October 1, 2018. (Photo by Carlo Allegri/Reuters)

A U.S. Army crew chief flying on board a CH-47F Chinook helicopter observes the successful test of flares during a training flight in Afghanistan, March 14, 2018. (Photo by Tech. Sgt. Gregory Brook/Reuters/U.S. Air Force)

House Minority Leader Kevin McCarthy (R-CA) and U.S. President Donald Trump watch a woman carry a card announcing the rounds during a mixed martial arts fight in Madison Square Garden in New York, New York, U.S., November 2, 2019. (Photo by Joshua Roberts/Reuters)

In this August 21, 2017 photo released by the U.S. Defense Department, Qatari special operations personnel conduct a military free-fall Friendship Jump over Qatar. The U.S. military has halted some exercises with its Gulf Arab allies over the ongoing diplomatic crisis targeting Qatar, trying to use its influence to end the monthslong dispute, authorities told The Associated Press on Friday, October 6, 2017. (Photo by Staff Sgt. Trevor T. McBride/ U.S. Air Force via AP Photo)

U.S Army combat camera photographer Spc. Hilda Clayton took this photo July 2, 2013 that was released by the U.S. Army, that shows an Afghan soldier engulfed in flame as a mortar tube explodes during an Afghan National Army live-fire training exercise in Laghman Province, Afghanistan. The accident killed Clayton and four Afghan National Army soldiers. (Photo by Spc. Hilda Clayton/U.S. Army via AP Photo)

For more than three years, Ukraine has been plagued by a conflict between the eastern secessionist territories and the Kiev government. Demonstrations by pro-Russian parties that oppose the current government first began in 2014 - and now, over 10,000 people have died, many of them civilians. These images portray a generation caught between war and peace. Many of them were born into the civil conflict dominating the country and are disorientated about their place in the world. Here: Youths during a party organised on a decommissioned bridge in Kiev. (Photo by Aude Osnowycz/The Guardian)

Haitians pull a car atop a pushcart in Port-au-Prince, October 11, 1994. The price of gasoline has fallen to about $6 US per gallon since U.S. forces occupied Haiti. Before, gasoline had cost as much as $10 U.S. per gallon. (Photo by Eric Draper/AP Photo)

On the second straight day of record-setting temperatures, Maddy Hacker is hoisted up by friend Jasmine Harper, both of McLean, Virgnia, as they attempt an acrobatic stunt in front of the U.S. Capitol in Washington, U.S., February 21, 2018. (Photo by Kevin Lamarque/Reuters)