A helicopter puts off the fire during a drill in an exhibition on air medical rescue in Miyun District of Beijing, captial of China, May 31, 2019. (Xinhua/Yang Guang)

A rescuer operates helicopter winch during a drill in an exhibition on air medical rescue in Miyun District, Beijing, captial of China, May 31, 2019. (Xinhua/Yang Guang)

A rescuer evacuates during a drill in an exhibition on air medical rescue in Miyun District, Beijing, captial of China, May 31, 2019. (Xinhua/Yang Guang)

A helicopter puts off the fire during a drill in an exhibition on air medical rescue in Miyun District of Beijing, captial of China, May 31, 2019. (Xinhua/Yang Guang)