India, Jan. 4 -- A day after strong surface winds improved Delhi's air quality by more than 100 points, prompting revocation of impositions under Stage-3 of the Graded Response Action Plan (Grap) to curb pollution, the city's air quality index (AQI) once again started slipping towards the "very poor" category. Shallow to moderate fog was also a contributing factor, which led to more than 60 flight cancellations at the Delhi airport.

The India Meteorological Department (IMD) has also issued a yellow alert for Sunday, warning people of a possible moderate to dense fog in multiple parts of the city.

"A yellow alert has been issued for Sunday. Moderate fog is likely to be observed in many places of the city, with dense fog in some isolated ...