In India, the smog was so thick it caused flight delays and blocked views of the Taj Mahal, and the Golden Temple, the holiest site in Sikhism, in Amritsar. 

Lahore, the capital of Pakistan's eastern province of Punjab, was rated the world's most polluted city on Thursday, in live rankings kept by Swiss group IQAir. Authorities 

How is the situation in northern India?
 

In India's capital New Delhi, pollution levels remained in the 'severe' category for a second day.

On Thursday, New Delhi scored 430 on an index of air quality maintained by the top pollution panel. Anything above 400 is marked "severe."

Despite visibility falling to zero in parts of north India, flight activities remained normal. Earlier, the Delhi airport authority warned low visibility might affect some flights.. Flight tracking website Flightradar24 showing 88% of departures and 54% of arrivals were delayed.

White clouds of smog delayed several flights across northern India on Wednesday. On the same day, the pollutants in the air in New Delhi surged past 50 times the World Health Organization's recommended daily maximum.

Come winter, northern India invariably faces a smog crisis due to seasonal crop burning, low winds, and falling temperatures. Officials also blamed humidity, vehicle emissions, and industrial activity for further exacerbating the pollution.

Lahore still most polluted city
 

The air pollution situation in Pakistan's Lahore remained dire, as it was ranked the world's most polluted city on Thursday, by Switzerland-based IQAir.

The air quality in Lahore is impacted by smoke from fires burnt illegally in India's farming states of Punjab and Haryana.

On Wednesday, Lahore and Multan were rated the two most polluted cities in the world. This was two days after UNICEF warned that the health of 11 million children there was at risk in the region.

How have the governments responded?
 

Authorities in Lahore shut schools, limited outdoor activities, and deployed mobile clinics to treat respiratory patients. Residents were asked to avoid unnecessary travel and wear face masks.

Across the border in India, New Delhi saw government trucks spraying water to briefly dampen air pollution levels.

Earlier this month, authorities unveiled a scheme to spray water mist using three small drones.