Delhi smog: How do pilots deal with low visibility?

Delhi's AQI rose to a hazardous 481 on Monday, causing dense fog that prompted low- visibility procedures to be initiated by the Delhi International Airport Ltd (DIAL), reported news agency PTI.

In a post on X, DIAL said, “Low visibility procedures are in progress at Delhi airport. All flight operations are normal at present.”

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Airport officials told a reporter, “The airport has put in place strategic measures to improve resilience and reduce disruptions during low visibility which includes equipping advanced CAT III ILS (instrument landing system) in the three runways.”

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They have also implemented approach in-lighting systems (ALS) along with the ILS that helps with precise landings in low visibility conditions and even helps them navigate at zero visibility and align their craft to the centreline of the runway.

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Low visibility procedures such as these are activated when visibility drops below certain thresholds, typically when the runway visual range (RVR) is less than 800 meters or cloud ceilings fall below 200 feet.

In recent instances, visibility levels have dropped below 100 meters, prompting the activation of these procedures.

Before the measures are implemented, appropriate testing of the initiatives is also completed and this information is communicated to the air traffic control and airline operators.

Airlines like IndiGo have issued advisories recommending that passengers allow extra travel time and check flight statuses before heading to the airport due to expected delays from fog conditions.

The India Meteorological Department has issued an orange alert in the national capital, predicting “dense” to “very dense fog” in Delhi and its surrounding regions.