New Delhi, Jan 31 (Agencies): After a gap of three weeks, dense fog returned at the IGI airport today disrupted the schedules of about 200 domestic and international flights, causing inconvenience to the passengers.

Besides, as many as 150 flights were delayed by half an hour to three hours, a Jet Airways flight from Abu Dhabi had to be diverted to Mumbai while two domestic flights -- of SpiceJet and Kingfisher -- from Mumbai had to be diverted to Lucknow and Jaipur respectively after runway visibility dropped to 50 metres early in the morning, an airport official said.

"Airlines had to cancel 13 domestic flights from and to the city. Also. most of the flights scheduled to depart after 5.45 AM were rescheduled," he added.

Fog started to descend on the airport around 3 AM forcing the airport authorities to implement low visibility procedures on third runway at 3.32 AM. Visibility at the main runway also started to deteriorate around 5.30 AM and authorities implemented the low visibility procedures at 5.45 AM.

The LVP remained in force till 12.30 PM during which 112 aircraft operated with the help of various categories of instrument landing system (ILS). During the eight hour and 58 minutes duration of LVP at third runway and six hour and 45 minutes on the main runway, 68 flights operated with CAT-IILS, 5 with CAT-II, 17 with CAT-IIIA and 22 with CAT-IIIB ILS.

Most of flights scheduled to depart early morning were delayed as the runway visibility dropped to 75 metres, far below the required minimum criteria of 125 metres for take-off
set by the DGCA, while the general visibility remained below 50 metres for about five hours.

The runway visibility hovered between 50 to 100 metres and there were hardly any take-offs, due to which there were inordinate delays in schedule of flights, the official said, adding between 7 AM and 8 AM only three flights took off.

The situation started to improve only after 10 AM, when the visibility started to improve and become 800 metres but the flights remained delayed due to cascading effect of the
early morning fog, the official said.