There was a fresh spell of CAT III dense fog at the airport on Monday night, which developed quickly and brought general visibility down to zero and the Runway Visual Range (RVR) to below 175 metre.

“Dense fog developed at the airport around midnight, bringing about a steep fall in RVR from 800 metre to 175 metre. CAT IIIB conditions continued uninterrupted till 9.30 am,” R K Jenamani, director-in-charge, IGI Met Department said.

The weatherman said the important feature of Tuesday’s fog — with western disturbances finally exiting the region— is of a standing type. “The moisture level has now reduced from 95 per cent yesterday to 65 per cent today,” Jenamani said.

Low Visibility Procedure (LVP) was initiated at 10 pm yesterday, when the Runway Visibility Range (RVR) dropped to 1,300 metre at Runway 28 and 800 metre at Runway 29. Passengers had a trying time as almost all flights were delayed for more than four hours. “I had an early morning Kolkata-bound flight to catch, but it has now been rescheduled to 12 noon,” said Hemant Sharma, a stranded passenger.

At least 200 flights were delayed, eight diverted, 12 rescheduled and one was cancelled. Officials said operations on Runway 29 were once again stalled due to fog and all departures and arrivals took place on Runway 28.

At least 183 flights (including 72 domestic arrivals, 59 domestic departures, 30 international arrivals and 22 international departures) operated during the LVP, which lasted till 11.30 am, said an official. Some CAT-III B compliant flights landed and took off under poor-visibility conditions in the morning, airport officials said. The situation began to improve after 11 am, when the visibility went up to 1,100 metre on the main runway.

Most of the morning flights to Coimbatore, Bangalore, Mumbai, Shimla, Lucknow, Aurangabad, Jaipur and Chennai were either cancelled or delayed, sources at the airport said.

On Monday, air-travellers were a relieved lot as a relatively clear sky, following a week of foggy conditions, allowed almost all flights to work as per schedule.

Since December 28, IGI Airport has seen 60 hours of dense fog.

“We are expecting Category III dense fog from 5 to 9.30 am on Wednesday. The situation is likely to improve in the next 48 hours,” Jenamani said.