CHONGQING — In Jieshi Town, southwest China’s Chongqing Municipality, a quadcopter with eight propellers descended slowly in front of a courier station. The downwash from its propellers drew crowds of onlookers who watched as the aircraft landed to deliver its cargo. “A 13-kilometer winding mountain road takes at least 25 minutes by car, assuming you are lucky enough to avoid traffic,” said Li Haitao, a drone operator for JD Logistics. “The drone flies straight there in just eight minutes.”Li is one of JD Logistics’ 10 drone pilots in Chongqing, navigating the city’s famously complex terrain to handle a surge in...