Dense fog delayed flights in Delhi on Monday, and a cold wave forced authorities to delay the reopening of schools for a week, as visibility dropped and cars turned on their hazard lights.
Indira Gandhi International Airport in the Indian capital asked passengers to contact their airlines for updates on flights.
“Due to dense fog, flight operations at Delhi airport may be affected,” it said on Twitter.
Data from private flight trackers showed that many flights were delayed.
The India Meteorological Department (IMD) has forecast “dense to very dense foggy conditions” in Delhi and many parts of northern and eastern states, such as Punjab, Haryana, Uttar Pradesh and Bihar, till Tuesday.