Nearly all flights arriving into and departing from Delhi were affected. About 453 domestic and 97 international flights were delayed.
Almost 23 flights were canceled, all of which were domestic flights, according to airport an official.
No take-offs could take place between 7:30 AM to 9:30AM, the official said. This was because runway visual range (RVR) was between 100-125 metres, while aircraft require more than 125 metres RVR for take off.
While planes could land in Delhi, they were delayed because of the unavailability of parking bays, which were occupied by aircraft waiting to take-off, the official said.
There were no diversions to nearby airports due to fog, according to the official.
"All departures were held up due to fog, arrivals not getting gates as all occupied by aircraft waiting to depart. Departures finally starting to happen now. Consequential delays expected through the day across the network," Kapoor tweeted.