Around 60 flights were delayed at the Kolkata airport on Monday due to poor visibility, an official said.

Due to dense fog, low visibility procedures (LVP) had to be implemented at the airport from 7 am, he said.

The ATC declares LVP when visibility falls below 800 metres. It is also activated when the cloud ceiling is below 200 feet.

According to the Director of Netaji Subhas Chandra Bose International Airport (NSCBIA), Pravat Ranjan Beuria, no traffic movement took place from 7.10 am to 9 am, and around 30 flight arrivals and 30 departures were delayed, the airport director said.

The visibility had dropped below the permissible limit for commercial aircraft operations on Monday morning, he said.

The Kolkata airport is equipped with CAT-III B Instrument Landing System (ILS), which allows compatible aircraft and CAT III B trained pilots to operate with visibility up to 50 metres.

However, the visibility at Kolkata airport turned close to zero on Monday morning, which ruled out operations completely till 9 am, the official said.

The last flight departed from the airport at 3.35 am after which the visibility dropped.

In addition, seven flights to Kolkata were diverted to other airports such as Bhubaneswar, Raipur, Hyderabad and Nagpur, he said.

All arrangements were made to facilitate the stranded passengers in the airport terminal, Beuria said.

He said that visibility conditions improved after 9 am, and the first flight to arrive at the airport was from Dubai at 9.04 am.

The initial delays on Monday, both incoming and outgoing, will have a consequential effect throughout the day, airport sources said.