Dutch “plane spotters” wait for landing fighter jets at the Air Force airfield in Jagel, Germany, 12 May 2014. (Photo by Carsten Rehder/EPA)

Afghan labourers work at a brick factory as the sun sets on the outskirts of Mazar-i-Sharif on May 12, 2014. The labourers work from dawn until dusk, producing approximately 20,000 bricks per day for domestic use and earning a daily wage of around 10 US dollars. (Photo by Farshad Usyan/AFP Photo)

An Afghan boy walks along an ancient wall on the outskirt of Mazar-i- Sharif on May 15, 2014. Afghanistan remains at war, with civilians among the hardest hit, as the Taliban wage an increasingly bloody insurgency against the government. (Photo by Farshad Usyan/AFP Photo)

A couple is silhouetted against the backdrop of N Seoul Tower, commonly known as Namsan Tower, in Seoul May 13, 2014. (Photo by Kim Hong-Ji/Reuters)

People walk on a pedestrian bridge over Brasil Avenue during 48-hours-long bus strike in Rio de Janeiro May 13, 2014. A new strike on public transport renewed concerns about services and public order one month before Rio and 11 other Brazilian cities play host to the upcoming World Cup soccer tournament. (Photo by Sergio Moraes/Reuters)

A San Marcos resident who did not evacuate watching flames near his home, in the San Diego county, California. (Photo by Stuart Palley/EPA)

An Afghan youth pushes a friend on a ice-cream cart, as the sun sets on the outskirts of Mazar-i- Sharif on May 16, 2014. Afghanistan remains at war, with civilians among the hardest hit, as the Taliban wage an increasingly bloody insurgency against the government. (Photo by Farshad Usyan/AFP Photo)

Rain runs down a pane of glass as a woman aboard a pony waits to guide a horse off the track during a workout session at Pimlico Race Course in Baltimore, Friday, May 16, 2014. The Preakness Stakes horse race is scheduled to take place on Saturday, May 17. (Photo by Patrick Semansky/AP Photo)

Pro-Russian gunmen guard a checkpoint outside Slovyansk, eastern Ukraine, Thursday, May 15, 2014. On Thursday, Ukraine's acting president, Oleksandr Turchynov, claimed the Ukrainian army destroyed an insurgent base in the city of Slovyansk and another one in nearby Kramatorsk, about 150 kilometers (95 miles) west of the Russian border. (Photo by Alexander Zemlianichenko/AP Photo)

People walk on a catwalk over the Brasil avenue during a 48-hour bus strike in Rio de Janeiro May 13, 2014. The strike renewed concerns about services and public order one month before Rio and 11 other Brazilian cities play host to the upcoming World Cup soccer tournament. (Photo by Sergio Moraes/Reuters)

Christ the Redeemer statue is silhouetted against the glow of the moonset in Rio de Janeiro, Brazil, Tuesday, May 13, 2014. As opening day for the World Cup approaches, people continue to stage protests, some about the billions of dollars spent on the World Cup at a time of social hardship, but soccer is still a unifying force. The international soccer tournament will be the first in the South American nation since 1950. (Photo by Felipe Dana/AP Photo)

A Pakistani man carries a charpai along a street on a rainy day in Lahore on May 13, 2014. (Photo by Arif Ali/AFP Photo)

Del Mar firefighters roll up hose after a day fighting wildfires Wednesday, May 14, 2014, in Carlsbad, Calif. More wildfires broke out Wednesday in San Diego County, threatening homes in Carlsbad and forcing the evacuations of military housing and an elementary school at Camp Pendleton. (Photo by AP Photo)