A thick shroud of fog over Delhi severely disrupted flights and train services for the third day on Thursday.

None of the three Calcutta-Delhi morning flights could take off because of reports of poor visibility at Indira Gandhi International Airport.

The Calcutta-Delhi flights operated by Indian Airlines were scheduled to leave Netaji Subhas Chandra Bose International Airport at 7 am, followed by those operated by Jet Airways and Air Sahara. Though the passengers had boarded the planes in time, the flights did not take off.

The first flight from Calcutta took off at 9.30 am after the sky over the Capital cleared a little.

Similarly, three Calcutta-bound flights were delayed in Delhi. The first flight from Delhi, scheduled to land at Calcutta at 9.30 am, reached at 2.30 pm.

As the fog thickened after Thursday evening, causing poor visibility at Delhi airport, the Indian Airlines authorities cancelled the Calcutta-Delhi flight scheduled to take off at 7.55 pm.

For the same reason, the Jet Airways flight from Delhi landed in Calcutta two hours behind schedule.

Air Sahara’s Calcutta-Delhi flight did not take off till 8 pm and the authorities were not sure it would take off at all. There is no information so far on the Delhi-Calcutta flight, scheduled to arrive at 7.30 pm.

Stranded passengers were angry with the airport authorities because they were not informed about the arrival and departure of Sahara’s flight. Many people, who came to the airport to receive their kin, waited in vain for hours.

Airport officials said traffic was disrupted because of the Delhi fog. The sky in Calcutta was more or less clear.

The Calcutta Met office said on Thursday that though there could be a slight fall in the minimum temperature, the sky will remain clear. However, British Airways has already rescheduled its Calcutta-London flight to avoid a possible fog factor.

On Wednesday, Indian Airline’s IC 202 Calcutta-Delhi flight could not land at Delhi airport because of the dense fog and had to return to the city.

Officials said if visibility at Delhi airport remained unchanged, the night flights would either have to be cancelled or rescheduled on Friday.

Several long-distance trains were stranded at different places because of the fog. As a result, a number of trains, including Rajdhani Express, ran far behind schedule.