After remaining normal for two days, operations at the Indira Gandhi International (IGI) airport here today were hit due to dense fog which affected schedules of over 50 flights.
Arrival or departure of around 20 flights were cancelled either due to operational reasons or due to bad weather conditions, airport officials said. Among the flights arriving here which were cancelled were from Bagdogra, Pune, Lucknow, Mumbai, Patna and Chandigarh.
Air India flight AI 996 from Dubai was diverted to Mumbai at around 4.50 AM, when visibility dropped below 50 metres, as the aircraft was not CAT-IIIB certified for instrument landing.
To operate in dense fog conditions, an aircraft has to be CAT-IIIB complaint along with its cockpit crew. The aviation regulator Directorate General of Civil Aviation has to certify an aircraft declaring it fit to operate under poor visibility conditions.
Fog started to descend at the airport last night and general visibility dropped to below 50 metres on the third runway around 3 AM, while visibility was around 1,000 metres on the main runway (28/10), when airport experienced very dense fog, the officials said.
But the situation changed within 40 minutes and visibility on the main runway dropped to 125 metres at one end, forcing the authorities to implement low visibility procedures (LVP).
The visibility remained around 100 metres on the third runway till 6 AM, which left it operational for arriving flights as the minimum visibility for take-off is required to be 125 metres and 150 metres for small and big aircraft.
The runway visibility started to improve around 8 AM and gradually increased to 200 metres and more.
LVP was finally lifted at around 11 AM when the visibility increased to 1,000 metres. A total of 95 flights landed assisted by various categories of instrument landing systems.
Operations at the airport had remained normal for the past two days even as it had witnessed moderate to shallow fog.