一架彩虹-4无人机6月中旬在我国西北某机场进行飞行训练。飞行前，空速管上套着保护罩，上面写着 “起飞前移除”。[陈博渊 / 摄]

A protective cover with a "remove before flight" notice is placed on the pitot tube of a CH-4 drone parking on the apron of an undisclosed airport in northwest China for a scheduled test flight in mid-June. [Photo by Chen Boyuan / China.org.cn]