At Delhi, the minimum runway visibility required for takeoff is 125 metres.
According to System of Air Quality and Weather Forecasting And Research (SAFAR), the overall Air Quality Index (AQI) was recorded at 283 till 9:45 am, which falls in the 'poor' category.
A fresh Western Disturbance would affect the Western Himalayan region from night of 15 January onwards followed by another on 18 January.
A senior Railways officer said nine trains have been delayed by an average of three hours due to fog.
Apart from chilly weather, the national capital also continued to reel under 'severe' air quality.
The minimum temperature in the national capital is predicted to take a dip by 1 degree Celsius and likely to freeze at 3 degree Celsius on Saturday.
All departures were stopped at 7.15 am and were resumed only at 9:16 am at the Indira Gandhi International airport.
The accident took place on the Jhajjar bypass, resulting in a pileup as multiple vehicles rammed into each other due to reduced visibility caused by dense fog in the area, police said.
The CISF ordered over 15,000 masks for its personnel deployed at IGI Airport, Delhi Metro and other government installations.
Primary schools to remain closed in Delhi on 8 October in view of the deteriorating quality of air in the city.