The runway visibility was good at night and operations were smooth but it started to deteriorate after 6.30 am and take-offs were suspended as runway visibility dropped to less than 125 metres, the required minimum for the low visibility take off (LVTO), an airport official said.
Planes arriving at Delhi airport were able to land using the CAT-III B instrument landing system (ILS), but it was also stopped as the visibility at the one end of the runway went below 50 metres at around 7.30 am, the official said.
Since the take-offs were suspended since 6.30 am, flights scheduled to depart after that have been put on hold due to which schedule of around 40 domestic and international flights has been delayed.
Also, around eight flights were cancelled or not operating out of Delhi to some destinations either due to operational reasons or poor weather conditions at the destinations, airport sources said.
The Delhi airport is equipped with CAT-III B ILS on two runways, which helps a CAT-III B compliant plane to land when the runway visibility is up to 50 metres.
Airport officials said, there might be a few diversions of flights today.Flight operations have been disrupted for past two days due to dense fog.
The city witnessed chilly winds, which also brought the temperature down.
Met department has predicted a mainly clear sky with possibility of moderate fog in the morning tomorrow. The maximum and minimum temperatures are likely to remain around 20 and seven degrees Celsius respectively.