Most of the time, temporary runways are rolled out on dirt slopes for takeoff and landing. Some runways are very narrow and are not as wide as aircraft wings, while others are on top of mountains.

"Our first consideration is not whether the working conditions are difficult, but whether the climate is conducive to the growth of seeds," said Song Zhanqing, a former pilot.

The difficult mission has born fruit over the years. Yulin city in Shaanxi province is located on the edge of the Mu Us Desert and has been forced to relocate three times throughout the years because of the frequent sandstorms.

In 2014, after more than 30 years of aerial seeding work, about 57.3 million hectares of drifting sand were put under control, and Yulin's vegetation rate rose from 1.5 percent to 45.2 percent, turning the city into a livestock product base and granary of the province.