Five international flights were diverted to nearby airports due to poor visibility.
The visibility at the main runway was between 150-175 metres, while at the new runway it was between 75-100 metres.
General visibility was less than 50 metres and some of the flights landed using CAT-IIIB instrument landing system, an airport official said.
With visibility dipping below the prescribed limit of 125 metres and 150 metres for different types of aircrafts, flights were not able to take off and were delayed by upto 5 hours.
Two Jet Airways flights from Dubai and Doha and two Air India flights from Muscat and Abu Dhabi and a Royal Jordan flight from Amman were diverted to nearby airports.
Four domestic flights to Lucknow, Kochi, Bangalore and Chandigarh were cancelled. The airport has been witnessing fog for the last three days due to which flight schedule has been badly affected.