Dense fog hits operations at Delhi airport, flights delayed

Dense fog on Monday disrupted operations at Delhi International Airport Ltd (DIAL) for about two hours, leading to delays and diversions of about 140 flights.

While 131 domestic and international flights recorded delays ranging between 30 minutes and three hours, nine flights had to be diverted to Jaipur (six), Ahmedabad (two) and Lucknow (one), as visibility at the runway fell below 50 metres. The visibility required for a CAT-III B-compliant aircraft to land using the instrument landing system (ILS) is at least 50 metres.

“Usually, the visibility required for landing at and departing from Delhi airport is 75 metres and 125 metres, respectively. With visibility dropping below 50 metres, operations were affected till around 9.30 am,” said a senior airline executive.

Fog started enveloping the airport early on Monday morning, and thickened around 6.30 am. No take-off or landing was recorded between seven am and 9.30 am.

Around 9:30 am, when visibility exceeded 50 metres, flights scheduled to land at the airport were instructed to land on the main runway (28/11), using CAT-III B ILS, as the visibility on the third runway was still poor. “But no flights were allowed to depart, as the minimum visibility requirement was 125-150 metres, depending on the size of the aircraft,” airport sources said. Runway 29/11 remained closed till around 12 pm.

To minimise delays this season, the Airports Authority of India and DIAL have put in place an integrated collaborative decision making  procedure, which involves airport operators, airlines, ground handlers and air traffic control collaborating and sharing data through an automated system. Airports officials expect the combined decision-making to help improve utilisation in winters, when fog is common.

The Met department has predicted 80-100 hours of fog, with 15-20 days of disruption, at the Delhi airport this year, against 140 hours last year. It added dense fog is likely after December 24-28, 2013. But with dense fog arriving early, flight schedules were affected today.