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.
Delhi's Chief Minister Arvind Kejriwal tweeted that pollution was "unbearable" across North India.
New Delhi has been ranked the most polluted city in the world, according to Greenpeace and AirVisual; a report by the two found that seven of the world's 10 cities with the worst air pollution are in India.
On Sunday, major airlines including Air India and SpiceJet warned of delays and cancellations to flights to and from the international airport.