An undercover police officer, who had been marching with anti-police demonstrators, aims his gun at protesters after some in the crowd attacked him and his partner in Oakland, California December 10, 2014. Police said more than 100 demonstrators marched in Berkeley, California, which has a history of social activism. Under cloudy skies, turnout was smaller than earlier in the week, when demonstrators in the area threw rocks at police and shut down a major freeway. (Photo by Noah Berger/Reuters)

Planes land in fog at Heathrow Airport, west London, as heavy fog covers a many parts of the south east, on April 1, 2014. (Photo by Steve Parsons/PA Wire)

Demonstrators perform a dance in front of riot policemen during a march called by students to request changes in the education system in Santiago, Chile September 5, 2017. (Photo by Ivan Alvarado/Reuters)

Workers look at exotic models and p*rn actresses standing on the top of a bus waving to people to promote the “Expo Sеx and Eroticism” adult exhibition in Mexico City, Mexico March 1, 2017. (Photo by Carlos Jasso/Reuters)

Japan's computer giant Fujitsu employee displays the world's first personal computer with Intel's RealSense 3D camera “FMV Esprimo” in Tokyo on October 9, 2014. The new desktop PC with 23-inch LCD display can make avatars which mimic the user's look and motion for chatting on the Internet. (Photo by Yoshikazu Tsuno/AFP Photo)

A woman looks towards part of an artwork called “Lichen! Libido! (London!) Chastity!” by Anthea Hamilton, one of the four artists shortlisted for the Turner Prize 2016, as it is displayed at the Tate Britain gallery in London, Monday, September 26, 2016. The Turner Prize aims to promote public debate around new developments in contemporary British art. (Photo by Kirsty Wigglesworth/AP Photo)

Bjorn, aged 5, smiles as he poses with a Owl butterfly during an event to launch the Sensational Butterflies exhibition at the Natural History Museum in London, Britain March 23, 2016. The exhibition opens to the public on March 24 and runs until September 11. (Photo by Dylan Martinez/Reuters)

Number 10. BELL H-13 SIOUX was a two-bladed, single engine, light helicopter built by Bell Helicopter. Westland Aircraft manufactured the Sioux under license for the British military as the Sioux AH.1 and HT. In 1947, the United States Air Force ordered the improved Bell Model 47A. Most were designated YR-13 and three winterized versions were designated YR-13A. The United States Army first ordered Bell 47s in 1948 under the designation H-13. These would later receive the name Sioux. The Bell-built H-13 B is seen airborne in this April 29, 1951 photo. The helicopter is equipped with a 173 horsepower engine, cruises at 85 miles per hour, climbs 900 feet in a minute and has a service ceiling of 11,500 feet. (Photo by AP Photo)