A passenger without pants waits for the subway train during “The No Pants Subway Ride” in Mexico City January 11, 2015. The event, the fifth organized in Mexico, is an annual flash mob and occurs in different cities around the world, according to its organisers. (Photo by Edgard Garrido/Reuters)

Members of the Royal Navy respond to a simulated fire in a Vanguard-class submarine control room training facility at Clyde naval base in Faslane, Scotland on January 21, 2016. (Photo by Photograph: Danny Lawson/PA Wire)

Hotel staff practice self-defence skills after a training session given by team member of Special Weapons and Tactics (SWAT) team, in Hangzhou, Zhejiang province, April 7, 2016. (Photo by Reuters/Stringer)

A golden eagle grabs a flying drone during a military training exercise at Mont-de-Marsan French Air Force base, Southwestern France, February 10, 2017. (Photo by Regis Duvignau/Reuters)

Syrian refugee and Olympic swimmer Yusra Mardini is pictured during a training session in a pool at the Olympic park in Berlin, Germany on April 26, 2018. (Photo by Fabrizio Bensch/Reuters)

Ukrainian emergency workers spray a plane with water hoses as part of a rescue training exercise at Boryspil International Airport outside Kiev, Ukraine, September 27, 2016. (Photo by Valentyn Ogirenko/Reuters)

A Belarussian border guard checks a passenger's passport in a train after it arrived from Lithuania, at the railway station Gudogai, Belarus, November 22, 2016. (Photo by Vasily Fedosenko/Reuters)

A horse grazes on railway tracks near the old train station on the the Northeast railroad (Ferrovia do Nordeste) in the city of Missao Velha, Ceara state, northeastern Brazil, October 25, 2016. (Photo by Ueslei Marcelino/Reuters)