After remaining free from fog for almost five days, flight operations were affected on Thursday morning as dense fog enveloped the IGI airport in New Delhi disrupting the schedules of over 35 domestic and international flights.
About 25 international and domestic flights were delayed by up to two to three hours while 10 domestic flights to Agartala, Mumbai, Bhubaneswar, Pune, Chennai, Leh, Amritsar, Lucknow and Coimbatore were cancelled due to the fog, airport sources said.
The airport had witnessed shallow fog during the day on Wednesday, but it did not disrupt the flight movements as visibility was manageable and there was no problem in landing and take-off till late evening.
Thick fog started to descend on the airport from around 11 pm last night, reducing the general visibility to zero and runway visibility to less than 100 metres, forcing the airport authorities to implement low visibility procedures and flights operated using CAT-III B Instrument Landing System (ILS).
After the runway visibility dropped to 500 metres last evening, pilots landed the aircraft using CAT-I instrument landing system.
"In the morning, the runway visibility was between 200 to 300 metres on both the runways which are CAT-III B compliant and can help an aircraft to land when the runway visibility is about 50 metres and flights were operating under CAT-III B conditions," an airport official said.
With no dense fog in the last five days, flight operations at the Indira Gandhi International Airport had remained uninterrupted.