Heavy smog has cancelled at least 20 flights at Beijing’s Capital International Airport  on Wednesday morning.
Eighteen domestic departures were also grounded, according to the BCIA website’s flight schedule, which was last updated at 9.45am.
The airport released a statement on its Chinese-language website saying severe haze would affect flight traffic until 10am.
It advised passengers to check the local weather report and to contact their airlines for the latest flight arrangements.
The US embassy’s air pollution index  reading for PM2.5 – or respiratory particulates smaller than 2.5 micrometres in diameter – stood at 434 per cubic metre that morning, a level considered to be hazardous.
The Beijing Meteorological Bureau issued a yellow alert for heavy fog on Tuesday, indicating visiblity had fallen to less than 100 metres.
Similar air and weather conditions have affected air traffic across northern China in the previous three weeks.
On Sunday, Beijing issued an orange fog warning  after visibility had fallen to less than 200 metres. Ten flights were cancelled the following day. Flights were also affected in Hebei, Hunan, Yunnan, Guizhou, Zhejiang, Jiangsu, Jilin, Heilongjiang and Sichuan provinces, with visibility reduced to about 100 metres at some airports.
Heavy snow  over the weekend forced the cancellation of 111 flights at BCIA, 16 of which were international. Nearly 70 flights were delayed on Sunday morning.