All morning flights to and from Netaji Subhas Chandra Bose International Airport in Calcutta were delayed for several hours by dense fog on Wednesday.

Air traffic schedules were disrupted for the third day this week. Schedules went haywire on Sunday and Monday, but the skies remained clear on Tuesday.

The fog cleared around 8.30 am on Wednesday and the first flight took off at 8.45 am, around four hours behind schedule. The Calcutta-Port Blair flight of Jet Airways was scheduled to leave at 5 am.

“A Jet Airways flight from Delhi was the first to land, at 9.50 am. All domestic flights were delayed, but none had to be cancelled or diverted,” an airport official said.

Around 4 am, runway visibility was reduced to below 50 m. The minimum visibility required for a flight to take off or land is 550 m.

Train services, too, were hit on Wednesday morning for 45 to 60 minutes. Among the long-distance trains that arrived late were Howrah-Mumbai Mail, Sambalpur Express, Gyaneswari Express, East Coast Express, Tundla Express and Gitanjali Express. “Gitanjali Express was delayed by more than four-and-a-half hours,” said an official.