Flight services were disrupted at the Calcutta airport on Thursday morning because of fog.

More than 60 flights were delayed, several cancelled and a dozen diverted as operations were suspended from 5am till 9.30am, when the visibility dropped below 50m, officials said.

“A fog is categorised as dense if the visibility drops below 200m. When the visibility is below 50m, it is called very dense fog,” said a Met official.

Dense fog is expected on Friday morning, too, the Met office said.

As many as 41 incoming and 21 outbound flights were delayed on Thursday morning.

Twelve flights were diverted. IndiGo’s flights from Bangalore and Delhi were diverted to Bhubaneswar and Ranchi, respectively. The airline’s flight from Bangkok was diverted to Bhubaneswar and an Emirates flight from Dubai was sent to Chennai.

Not just in Calcutta, fog disrupted flights in Bagdogra, too. “Ten flights were cancelled and five were diverted,” said an official at the Bagdogra airport.

A combination of moisture, clouds and light wind contributed to the formation of the dense fog, said a Met official.

The moisture is being provided by the anticyclonic flow of winds from the Bay of Bengal, the official said. Moisture-laden winds are dominating the lower level of the atmosphere, he said.

The Calcutta airport has the Category IIIB instrument landing system that allows aircraft to operate even when the visibility is as low as 50m. However, from 5am till 9.30am, the visibility had dropped below 50m, leading to the closure of airport operations, an airport official said.

Many passengers were stranded at the airport.

Kasba resident Sripom Sinha was to fly to Delhi and from there to Amsterdam. The Air India flight to Delhi was to leave at 7.20am and the airline’s connecting flight to Amsterdam at 2pm.

“We boarded the flight at 6.40am. Around 7.25am, the pilot announced that there would be a delay because of fog,” said Sinha, an IT professional who stays in
Amsterdam.

Around 8am, the passengers were asked to get off the aircraft.

“I would have missed the connecting flight from Delhi. So I decided to cancel the tickets,” Sinha said.

He had to wait till 12.30pm before he got back his luggage.

“I had booked the tickets for ₹42,000. Now I have booked tickets on another airline for ₹51,000,” he said.

A woman from north Calcutta, who had booked an IndiGo ticket to Ahmedabad for the Coldplay concert on January 25, faced harassment.

Though the flight was in the afternoon, she received a message from the airline that it had been cancelled because of fog.

“… due to consequential effect of bad weather at Kolkata Airport, your flight 6E 798 from CCU to AMD on 23 January 2025 is cancelled. We understand that this might impact your travel plans and apologize for the inconvenience that this may have caused,” the message from IndiGo said.

“Our son and daughter were booked on an evening flight to Ahmedabad. That left at the scheduled time. We asked a friend in Ahmedabad to pick them up,” said the woman’s husband.

She had booked her ticket for around ₹7,500. On Thursday, she had to rebook on a Friday flight for around ₹16,000, the husband said.

Trains impacted

Poor visibility affected trains, too. Trains in Eastern and South Eastern Railway moved at a much slower pace than usual in the morning because of reduced visibility.

“Digha, Panskura, Shalimar and many other sections reported long delays in the arrival and departure of local trains. Several long-distance trains were also delayed. The Howrah-bound Rajdhani and Duronto were among them,” said a railway official.

“The visibility had dropped so much that loco pilots were not able to see beyond a few hundred metres. That is why the speed had to be controlled,” the official said.