KUNMING, May 1 (Xinhua) -- A drone found at the clearance protection zone of an airport in southwest China's Yunnan Province forced 32 flights to land at alternative airports or return on Monday.

Sources with Kunming Changshui International Airport in the provincial capital said the drone was found by crew members on board a plane when it was about to land around 2 p.m. The drone incident has left 28 flights to return and four to land at alternative airports.

The airport resumed normal operations after 3 p.m.

Since Feb. 2, 2017, the airport has been bothered by at least six drones incidents. The local police have launched investigations.

In late April, four drones flown illegally over Chengdu Shuangliu International Airport in southwest China's Sichuan Province, which forced 58 flights to land at alternative airports, four flights to return, and more than 10 to be canceled.