A train attendant helps a passenger to adjust her seat at the business class carriage on a CRH 380A bullet train Thursday, June 16, 2011. (Photo by Reuters/China Daily)

People carry lychee for sale on a motorbike on a street in Luc Ngan, Bac Giang province, Vietnam, 22 June 2016. Lychee output in Bac Giang province is expected to reach 130,000 tonnes this year. China is still Vietnam's main lychee export market so far, buying around 60 percent of the annual crop, according to official reports. (Photo by Luong Thai Linh/EPA)

A U.S. Army B-24 Liberator Bomber is hailed by a ground crewman as it takes off over a line of shark- nosed fighter planes at an advanced base in China on a mission on October 10, 1943, to bomb Japanese installations. (Photo by AP Photo)

Vladimir Putin looks at a model of the Tupolev TU-160 bomber, or Blackjack, that was presented to him on his arrival in Olenegorsk, Russia, August 16, 2005. Putin flew in the Tupolev TU-160 bomber and took part in the launch of cruise missiles in the Arctic north. (Photo by Reuters/ITAR-TASS/Presidential Press Service)

Fire photographer Tod Sudmeier gets hit with flying embers from strong winds at the Solimar brush fire that started early Saturday morning in Ventura County, California December 26, 2015. (Photo by Gene Blevins/Reuters)

A vendor drinks water as she waits for customers at a roadside flower market in Ahmedabad, India, February 8, 2017. (Photo by Amit Dave/Reuters)

Cockpit of a SCG 0003S racecar is seen during the 87th International Motor Show at Palexpo in Geneva, Switzerland March 8, 2017. (Photo by Arnd Wiegmann/Reuters)

Attendees wear a cardboard “Facebox” at the 2017 South By Southwest (SXSW) Interactive Festival at the Austin Convention Center in Austin, Texas, U.S., on Monday, March 13, 2017. The SXSW Interactive Festival features a variety of tracks that allow attendees to explore what's next in the worlds of entertainment, culture, and technology. (Photo by David Paul Morris/Bloomberg)