to a complete halt around 10 PM after runway visibility dipped to less than 75 metres, which is the minimum required visibility condition for an aircraft to land using CAT IIIB instrument landing system.
The general visibility was almost nil. The minimum required visibility for an aircraft for the Low Visibility Take Off (LVTO) is 125 metres and 150 metres, depending upon the size of the aircraft. Delhi airport is equipped with two CAT-III B complaint
runways, which enables a CAT-III B trained pilot to land a CAT-III B complaint plane when the runway visibility is merely 75 metres.
Yesterday, the visibility remained poor during the whole day which led to delay in schedule of around 206 domestic and international flights.
Flight operations resumed today around 1 AM, when the landings started. Priority was given to international flights, as most of them operate at night, they said.
Though the visibility was poor, planes were landing using CAT III B ILS and the take off started around 4 AM, when runway visibility improved to more than 150 metres on the main runway (28/10), officials said.
But gradually visibility on the third runway, (29/11) also started to improve and both the runway were used intermittently, they added.
Delhi had been witnessing dense fog from Saturday last, which, according to the Met Department, is the "season's worst". Met officials said it may be the worst fog after January 2010.