Photo taken by a smart phone on Dec. 17, 2016 shows a plane arriving at the Beijing Capital International Airport in Beijing, capital of China. Beijing activated its first red alert for smog this winter on Friday. The sky was gray across much of north China on Saturday as at least 24 cities, including Beijing and Tianjin, have activated red alerts to address the pollution. The measures included car restrictions on roads, suspension of construction and classes for kindergartens and primary schools as well as reduced emissions for factories. (Xinhua/Chen Jianli)