Did your flight get delayed due to fog? How does Delhi airport tackle it?

This creates a ripple effect on flight operations: the crew which was supposed to fly the aircraft can run out of their allowed duty timings; a flight which was supposed to be used on a specific route is delayed or diverted to another airport, which means the airline has to arrange alternative aircraft; or restrictions on night operations come into place at the destination airport.

This creates a backlog of scheduled flights, which can take several hours to clear.

What are the measures in place to ensure smooth flight operations?

The aviation ecosystem has different visibility parameters, which dictate and limit the minimum visibility in which aircrafts can land. They also utilise Instrument Landing Systems (ILS), precise guidance systems which help aircrafts land in low visibility conditions.

They are of different categories.

CAT III (short for category 3) is the most advanced category of such systems, which allows aircraft landing in extremely low or near-zero visibility using advanced/autoland systems. These systems can operate with a runway visual range (RVR) below 300 metres. RVR refers to the distance a pilot can see runway markings or lights along the runway during take-off or landing.

CAT II systems allow landing with RVRs between 300 and 549 metres, while CAT I is for landings with RVRs above 550 metres.

For a flight to operate in CAT III conditions, an aircraft has to be equipped with specific gear, a pilot has to be trained for such operations, and the runway at the airport needs to have advanced technological equipment.

There are three different tiers of CAT-III ILS, too: A, B and C.

A is the most basic one, while C is the most advanced one, with CAT-IIIC compliant systems able to land aircrafts with zero visibility.

What equipment does Delhi airport have?

Delhi airport has four runways: 27-09, 28-10, 29R-11L and 29L/11R. Three of them are CAT-IIIB compliant at both ends, and the fourth one is CAT-I compliant.

But flight operations still get impacted during low visibility conditions as certain aircraft or pilots may not be CAT-III compliant. India’s aviation regulator, the Directorate General of Civil Aviation (DGCA), bars flights from taking off when the visibility falls below 125 metres; in such cases flights are usually diverted to other airports, and fuel is not an issue since aircrafts operate with additional fuel in such weather.

Currently, six Indian airports — Delhi, Lucknow, Jaipur, Amritsar, Bengaluru and Kolkata — are equipped to handle CAT IIIB operations.

India does not have a single airport capable of CAT IIIC operations. Airports such as New York’s John F Kennedy Airport and London’s Heathrow Airport support CAT IIIC landings.