Cooks prepare food for passengers on the Beijing-Lhasa train Z21, Oct. 7, 2015. From its operation on July 1, 2006 to Sept. 30, 2015, the Beijing-Lhasa train has carried 9.29 million passengers in a total distance of 31.03 million kilometers. (Xinhua/Tang Zhaoming)

Attendant Qu Zhenzhuang pours water for a passenger on the Beijing-Lhasa train Z21, Oct. 7, 2015. From its operation on July 1, 2006 to Sept. 30, 2015, the Beijing-Lhasa train has carried 9.29 million passengers in a total distance of 31.03 million kilometers. (Xinhua/Tang Zhaoming)

Captain Liu Yang (2nd R) talks with passengers on the Beijing-Lhasa train Z21 Oct. 7, 2015. From its operation on July 1, 2006 to Sept. 30, 2015, the Beijing-Lhasa train has carried 9.29 million passengers in a total distance of 31.03 million kilometers. (Xinhua/Tang Zhaoming)

Passengers board the Beijing-Lhasa train Z21 at the Naqu Railway Station in Naqu, southwest China's Tibet Autonomous Region, Oct. 7, 2015. From its operation on July 1, 2006 to Sept. 30, 2015, the Beijing-Lhasa train has carried 9.29 million passengers in a total distance of 31.03 million kilometers. (Xinhua/Tang Zhaoming)