A police helicopter hovers over the city during its routine patrol aviation for the tightening the orderly security guarding for the grand celebration of the National Day, in Zhengzhou, central China's Henan Province, Sept. 23, 2009. (Xinhua/Liu Shuting)

A police helicopter hovers over the city during its routine patrol aviation for the tightening the orderly security guarding for the grand celebration of the National Day, in Zhengzhou, central China's Henan Province, Sept. 23, 2009. (Xinhua/Liu Shuting)

A police helicopter flies over the tip of an edifice during its routine patrol aviation for the tightening the orderly security guarding for the grand celebration of the National Day, in Zhengzhou, central China's Henan Province, Sept. 23, 2009. (Xinhua/Liu Shuting)