Visibility was so poor that 37 flights — including at least one international journey — were diverted from the city’s Indira Gandhi International Airport, a senior airport official told CNN.
Pollution indexes saw air quality in the Indian capital climb to “hazardous” levels in the city on Sunday.
On Sunday, major airlines including Air India and SpiceJet warned of delays and cancellations to flights to and from the international airport.
The senior airport official told CNN that although planes can land during times of poor visibility, not all pilots are trained to do so.
“During winter months, when it’s foggy early in the morning and at night, and the visibility is poor, we have a roster of pilots who are experts to land in those conditions, so the schedules are made keeping in mind low visibility. That is something we can plan for,” he told CNN.
“But the visibility dropping suddenly due to pollution — that’s not something we plan for when making pilot’s schedules,” he said.
The official said conditions had improved somewhat later in the day, allowing some flights to resume.
Pollution in the city worsens at this time of year as temperatures drop and farmers light fires to clear their land.
Smog has blanketed much of the city in recent days, severely reducing visibility, restricting traffic and limiting all but the most necessary outdoor activities.
Schools in the area have been ordered to stay closed until Tuesday, according to the AFP news agency.
CNN’s Julia Hollingsworth and Manveena Suri contributed to this report.