Sudden dense fog at the IGI airport on Thursday brought air operations to a standstill for about three hours, leading to a delay of around 150 domestic and international flights, diversions of 18 and cancellation of four others.
Flight operations came to a standstill between 7 AM and 10 AM as the runway visibility was far below the required minimum range of 125 metres for low visibility take offs.
Poor runway visibility, which dropped to 50 metres at one point of time, delayed the departure of about 60 morning flights while 18 incoming flights had to be diverted to Ahmedabad, Jaipur, Amritsar, Chandigarh and Lucknow, airport sources said.
Four domestic flights were cancelled. The cascading effect was observed till evening when the total number of delayed flights crossed 150, an airport official said. Fog started to descend upon the airport around 4 AM and it started to become dense around 4.30 AM.
At 4.44 AM, airport authorities implemented the low visibility procedure on both the runways, which continued till 11.35 AM. During this, a total of 120 flights landed using various categories of instrument landing system. A total of 49 flights operated with CAT-I, while 14 used CAT-IIIA and 57 used CAT-III B ILS.
The runway visibility started to drop below the required LVT of 125 metres around 7 AM, delaying many flights. Passengers were a harried lot as the airlines had allowed them to board the aircraft without anticipating that the fog might thicken.
Some of them had to spend more than three hours in the planes as their aircraft were parked on the taxiway and could not take off due to poor visibility.
"We were at the runway since 6.50 AM and at 9.40 AM, the pilot announced that we need refuelling now, as they had burned the fuel at the taxiway, what a waste of precious fuel," said Rajesh Nagar, a passenger who boarded a Jet Airways flight to Chennai.
Some of the passengers, who only had cabin baggage with them, cancelled their journey and deboarded the plane.