A thick blanket of fog descended on Delhi on Sunday night, severely affecting air and road traffic.
Airport sources said the last domestic flight to land was at 2033 IST. All landings and take-offs were halted at 2100 IST, when the Runway Visibility Range was reduced to a mere 100 metres.
The first international flight to land on Monday was at 0913 IST; a flight to Chennai took off at 0939 IST, officials said.
Though the night temperature was 9.4 degree Celsius, one degree above the normal, the northwesterly wind accompanied by moisture from Punjab resulted in condensation, thus causing fog, the meteorological office said.
The Met office also said visibility on the roads had gone below 400 metres.