Schedules of over 170 flights were disrupted due to dense fog that enveloped the IGI airport on Wednesday.
As the runway visibility started to deteriorate due to fog, six domestic and six international flights were diverted.
About 20 domestic and international flights were cancelled while several others were delayed by up to three to four hours, causing inconvenience to passengers.
An Emirates flight (EK 513) which scheduled to depart at 4.15 am on Wednesday was delayed by over 15 hours due to bad weather conditions.
Passengers and crew of the flight had to be disembarked and offered hotel accommodation. The flight was rescheduled for departure at 9.15 pm.
Fog started to descend on the airport on Tuesday night and it become very dense at around 10.30 pm when the general visibility dropped to zero and the runway visibility to less than 100m.
The condition worsened in the morning when the runway visibility dropped to 75m for both, main and new, runways.
Dense fog also enveloped the airport from 8.30 pm on Wednesday, disrupting schedules of 13 domestic flights. Two non-stop Air India flights to New York and Frankfurt were also rescheduled due to the late evening fog.
Very few flights, which operated using the CAT-III B instrument landing system, had arrived or departed since morning due to the poor visibility at the airport, an official said.
During the low visibility procedure, which was implemented at 1.02 am and finally withdrawn at 11.38 am, a total of 125 flights were operated using various instrument landing systems.
About 62 flights operated with CAT—I ILS, while seven with CAT—II, 33 with CAT—III A and 23 using the CAT-III B ILS, the official said.
The airport has been witnessing dense fog since last Wednesday, affecting the schedule of over 350 flights.