Photo taken on Oct. 16, 2018 shows construction site of Lhasa-Nyingchi railway in southwest China`s Tibet Autonomous Region. Infrastructure has been improved in Tibet, as a comprehensive transportation network composed of highways, railways and air routes has been formed. (Xinhua/Purbu Zhaxi)

Aerial photo taken on Jan. 11, 2019 shows a road leading to Lhasa, southwest China`s Tibet Autonomous Region. Infrastructure has been improved in Tibet, as a comprehensive transportation network composed of highways, railways and air routes has been formed. (Xinhua/Purbu Zhaxi)

Photo taken on Oct. 16, 2018 shows construction site of Lhasa-Nyingchi railway in southwest China`s Tibet Autonomous Region. Infrastructure has been improved in Tibet, as a comprehensive transportation network composed of highways, railways and air routes has been formed. (Xinhua/Purbu Zhaxi)

A tourism helicopter takes off in Lhasa, southwest China`s Tibet Autonomous Region, March 20, 2019. Infrastructure has been improved in Tibet, as a comprehensive transportation network composed of highways, railways and air routes has been formed. (Xinhua/Jigme Dorje)

Photo taken on Nov. 9, 2015 shows a mountain road in Ali, southwest China`s Tibet Autonomous Region. Infrastructure has been improved in Tibet, as a comprehensive transportation network composed of highways, railways and air routes has been formed. (Xinhua/Xiang Wenjun)

Performers give a dance performance beside a plane of the Tibet Airlines which prepares to take off at the Lhasa Gonggar Airport, southwest China`s Tibet Autonomous Region, July 26, 2011. Infrastructure has been improved in Tibet, as a comprehensive transportation network composed of highways, railways and air routes has been formed. (Xinhua/Chogo)