100 flights delayed, 2 diverted as dense fog envelops Delhi

At least 100 flights were delayed and two were diverted at Delhi’s India Gandhi International Airport due to dense fog early Tuesday morning when the visibility dropped to less than 200 metres.

According to airport officials, two flights -- SpiceJet flight at around 11.45 pm, and an IndiGo flight at 2.15 am – were both diverted to Jaipur, and added that these are the first diversions due to fog this season.

“In both cases, the pilots were not CAT-III B compliant and therefore, were not given permission to land at the airport. During this period, visibility was around 50 metres and the ATC guided both flights to the nearest airport, which is Jaipur,” said an airport official.

The airport initiates low visibility procedures (LVP) -- measures aimed at making landing for flights easier, when visibility dips below 800 metres. During this period, CAT-I procedures are in place, which is the most basic set of precautions to guide pilots in landing. Only flights and pilots that are CAT-II compliant are allowed to land when visibility is less than 550 metres, while CAT-III A pilots can land when visibility is between 175 and 300 metres. CAT-III B are the most stringent qualifications for a pilot to land a flight, allowing them to land even when visibility is 50 metres.

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While flights can still land at the airport when visibility is 50 metres, no flights are allowed to depart unless runway visibility range (RVR) is 125 metres. “This led to some arrivals and departures being delayed,” an official said.

A Met official said visibility was at its worst at the airport between 3.30 am and 7.30am, mostly in the range of 50 metres, before gradually improving to 100 metres by 7.30am. “During this four-hour window, visibility at both Palam and Safdarjung was 50 metres, with CAT-III B procedures in place. It increased to 100 metres at 7.30am and then increased substantially to over 500 metres by 9.30am,” the official said.

A change of over 15 minutes from the scheduled time of arrival or departure is classified as a ‘delay’.

Forecasts show Delhi is likely to see moderate to dense fog in the next two days as well, with visibility expected to drop down to 200 metres in parts of the capital.