Bhubaneswar, Jan. 4: This morning, thick fog disrupted flights at the city airport that had helped Calcutta airport overcome a similar crisis last month.

A chartered flight could not land here shortly after 10am and had to return to Rourkela. Last month, two passenger aircraft were diverted to Calcutta because of bad weather conditions here.

Ironically, 24X7 emergency airport operations at Biju Patnaik Airport here helped the flight operations at Calcutta airport by allowing two passenger aircraft on December 21 and 29 to land here when landing conditions were unsuitable in the Bengal capital.

An Indian Meteorology Department official said dense fog was because of the slow airflow on the landmass with a lot of moisture coming from the sea.

“Generally, the faster airflow from the landmass counters the moisture-laden air from the sea. But since the air speed is now less than 10kmph, the fog density is more now. It is likely to intensify in the next 24 hours,” the official said.

Airport director Sharad Kumar said: “The chartered King Air flight from Rourkela could not land here this morning because of thick fog. We have a Category I landing system in place, but all aircraft do not have the required equipment to read CAT I radar signals.”

Airports Authority of India (AAI) sources said when the aircraft from Rourkela was sent back this morning, visibility was 800 metres. However, the visibility level changes as the day progresses or the moisture level in the low-level clouds differs.

Thick fog has been observed in the city over the past two days. Visibility is likely to drop to 200 metres by Saturday.

On December 10 and 11 one scheduled flight on each day was diverted to Calcutta as the visibility level was low here.

Biju Patnaik Airport is equipped with CAT I landing system in which the minimum visibility level is 500 metres. CAT II and III are improved versions of this system that can negotiate visibility of 250m and 50m respectively.

The Calcutta airport is equipped with a CAT II landing system.

“However, despite having an advanced system in place, dense fog sometimes affects landing in Calcutta. For this reason, we are operating 25X7 now. It started on December 15 and will continue till February 15 and so far we have received two flights from Calcutta. The practice started from last year and we are ready to handle domestic and international flight diversions,” said the airport director.

“For this, we have to open our restaurant, waiting lounge, cafeteria and all other facilities for passengers when the emergency landing is done,” he said.