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)

A girl holds up a photo of Pope Benedict XVI which reads “tear his face” during a protest against the World Youth Day 2011 celebrations taking place on August 17, 2011 in Madrid, Spain. Initiated by Pope John Paul II in 1985, World Youth Day youth-oriented events for the celebration of the Catholic faith are held every three years in a different country; this time in Madrid from August 16 – 21, with Pope Benedict XVI in attendance. (Photo by Denis Doyle/Getty Images)

The first tram is delivered to the Gogar tram depot on October 17, 2011 in Edinburgh, Scotland. The tram was delivered on a low loader which had driven from Irun, northern Spain and is the first of 27 trams expected to arrive at the depot over the coming months. Last month the Scottish Government intervened to oversee the troubled Edinburgh trams project assigning project managers from Transport Scotland to work with contractors Bilfinger Berger. (Photo by Jeff J Mitchell/Getty Images)

Animal rights activists from the group “Animal Equality” are covered with plastic sheets to represent meat packaging as they stage a protest during “Day Without Meat” event in Barcelona, Spain, on March 20, 2013. (Photo by Lluis Gene/AFP Photo)

“Two Brothers”. We found about 20 lions eating a buffalo. When the male leaved the group we anticipated him to take photos. It is 8AM, light is perfect and the position too. The lion stops and looks down from the hill, another lion is coming up, it stiffens, I think that will be a fight, i'm tense, the camera is OK, the shots previously made perfect. The two meet, looking directly into their eyes, they sniff, rub against their heads, the tension drops, they start walking with the same step as when they were puppies, they are two brothers. Photo location: Masai Mara, Kenya. (Photo and caption by Massimo Mei/National Geographic Photo Contest)

In this March 7, 1991 file photo, a U.S. Marine patrol walks across the charred oil landscape near a burning well during perimeter security patrol near Kuwait City. Twenty five years after the first U.S. Marines swept across the border into Kuwait in the 1991 Gulf War, American forces find themselves battling the extremist Islamic State group, born out of al-Qaida, in the splintered territories of Iraq and Syria. The Arab allies that joined the 1991 coalition are fighting their own conflicts both at home and abroad, as Iran vies for greater regional power following a nuclear deal with world powers. (Photo by John Gaps III/AP Photo)

Gymnast Ahmad al-Sawas performs gymnastic moves near damaged buildings in the rebel-held Bustan al-Qasr neighbourhood of Aleppo, Syria March 26, 2016. As Syrian gymnast Ahmad al-Sawas watched his country fall apart, his Olympic dream collapsed too. The last national champion before the fighting began, he knew that supporting the anti-government side in the five-year-old civil war would prevent him from being selected for the Rio Games. (Photo by Abdalrhman Ismail/Reuters)