A Felix Airways plane is seen after it was destroyed by an airstrike at the international airport of Yemen's capital Sanaa, April 29, 2015. Jets from a Saudi-led alliance destroyed the runway of Yemen's Sanaa airport on Tuesday to prevent an Iranian plane from landing there, Saudi Arabia said, as fighting across the country killed at least 30 people. Airport officials said the strikes set a civilian aircraft operated by Yemeni Felix Airways ablaze. (Photo by Khaled Abdullah/Reuters)

Julian, left, is photographed by his mother with friend Gianluca, right, under water at a public pool in Gelsenkirchen, Germany, on a hot Friday, July 3, 2015. Germany faces a heat wave with temperatures up to 38 degrees Celsius (100 degrees Fahrenheit) at the weekend. (Photo by Martin Meissner/AP Photo)

A boat is stranded on Poyang Lake in Lushan City, China during low-water season on November 3, 2016. (Photo by Xinhua/Barcroft Images)

An American flag is visible in the windows of the cupola aboard the International Space Station. Thanks to a bill passed by Texas legislators in 1997 that put in place technical voting procedure for astronauts – nearly all of whom live in Texas – they have the ability to vote from space through specially designed absentee ballots. To preserve the integrity of the secret vote, the ballot is encrypted and only accessible by the astronaut and the county clerk responsible for casting the ballot. (Photo by NASA)

A dirty thunderstorm occurs over Mount Sakurajima as the volcano erupts violently at 12:03 am on July 26, 2016 in Tarumizu, Kagoshima, Japan. The eruption occurred at the mountain's Showa crater. This is the first time that the active volcano in southern Kyushu has spewed out a smokestack that high since an eruption on August 18, 2013, according to the Kagoshima Meteorological Office. (Photo by The Asahi Shimbun via Getty Images)

Fireworks explode over the Kremlin in Red Square which was blocked by police during New Year celebrations in Moscow, Russia, Sunday, January 1, 2017. New Year's Eve is Russia's major gift-giving holiday, and big Russian cities were awash in festive lights and decorations. (Photo by Alexander Zemlianichenko Jr./AP Photo)

A woman prays while touching the fingers of a Buddha statue during the annual Makha Bucha Day, which celebrates Buddha's teachings, in Ang Thong, Thailand February 11, 2017. (Photo by Jorge Silva/Reuters)

Students training to be flight attendants hold books on their heads, chopsticks in their mouths, and papers in between their knees, as they take part in a standing posture practice at a vocational school in Shijiazhuang, Hebei province, China May 4, 2017. (Photo by Reuters/Stringer)