A group of J-7 fighter jets attached to a brigade with the PLA Air Force Xi'an Flight Academy taxi on the runway in formation during a flight training course near the Qilian Mountains in northwest China's Gansu Province on September 20, 2018. (Photos: eng.chinamil.com.cn)

A J-7 fighter jet attached to a brigade with the PLA Air Force Xi'an Flight Academy takes off for a sortie during a flight training course near the Qilian Mountains in northwest China's Gansu Province on September 20, 2018.

A pilot cadet assigned to a brigade with the PLA Air Force Xi'an Flight Academy gets settled in the cockpit of a J-7 fighter jet prior to a flight training course near the Qilian Mountains in northwest China's Gansu Province on September 20, 2018.

A maintenance man assigned to a brigade with the PLA Air Force Xi'an Flight Academy helps a pilot cadet to go through pre-flight inspections prior to a flight training course near the Qilian Mountains in northwest China's Gansu Province on September 20, 2018.

A pilot cadet assigned to a brigade with the PLA Air Force Xi'an Flight Academy gets settled in the cockpit of a J-7 fighter jet prior to a flight training course near the Qilian Mountains in northwest China's Gansu Province on September 20, 2018.