Romanian military doctors and medical students sit on a bus behind steamy windows before the National Day parade in Bucharest, Romania, Thursday, December 1, 2016. Military planes and helicopters flew over the Romanian capital Thursday as thousands turned out to celebrate the national day, marking the date when the country reunified with Transylvania in 1918. (Photo by Vadim Ghirda/AP Photo)

Promotional models use their smartphones during their break at the Global Mobile Internet Conference in Beijing May 6, 2014. Mobile Internet industry executives, developers and investors from more than 30 countries took part in the Global Mobile Internet Conference in Beijing, the organiser said. (Photo by Kim Kyung-Hoon/Reuters)

A believer dressed as a “diablo” (devil) jumps at the San Blas' (Saint Blaise) procession during the “Endiablada” festival in Almonacid del Marquesado, in central Spain February 3, 2015. In the “Endiablada”, an undated traditional festival in honour of the Candelaria Virgin and San Blas, believers are dressed in colourful costumes, wear a mitre with lead cowbells tied to their waists that ring as they wander around the village and in front of the saints' statues during their processions. (Photo by Susana Vera/Reuters)

A tribal fighter loyal to Yemen's government stands in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)

Filipino beauty candidates hide from the sun before a group photo during the media presentation of the Miss Philippines Earth 2017 held at a hotel in Manila, Philippines, 05 July 2017. A total of 40 environmentally aware and concerned Filipino young ladies will compete to represent the Philippines at the Miss Earth beauty pageant. Miss Earth is a pioneering beauty pageant that serves as a vehicle for environmental advocacy. (Photo by Mark R. Cristino/EPA)

Labourers unload gravel from a boat docked in Dala township, opposite Yangon city, Myanmar, November 12, 2015. (Photo by Olivia Harris/Reuters)

People take pictures of huge waves crash on the Viavelez seafront in the northern Spanish region of Asturias January 2, 2016. (Photo by Eloy Alonso/Reuters)

Over 30 Douglas C-47 Skytrains (Dakotas) making final preparations for flight formation practice before the 75th D-Day Anniversary flight to Normandy in Duxford, England on June 4, 2019. (Photo by UK Air Force Images)