Why Fog Grounds Delhi Flights: CAT III Landings Explained (2026)

Updated July 2026 · HappyFares

Every winter, north India wakes up to the same headlines: hundreds of flights delayed at Delhi, passengers stuck on aprons, and a word most travellers only half understand, CAT III. Here is what the categories actually mean, and why a CAT III airport still cancels flights.

What do CAT I, CAT II and CAT III actually mean?

They are categories of instrument approach, defined internationally by ICAO and adopted in India by the DGCA. Each category describes how low the cloud base and how poor the runway visual range (RVR) can be before an approach must be abandoned. CAT I is the everyday approach flown in normal weather. CAT II and CAT III step those limits progressively lower.

The two numbers that matter are decision height, the point on the approach at which the crew must either see enough of the runway environment to continue or go around, and RVR, a machine-measured estimate of how far a pilot can see along the runway. Sensors placed near the touchdown zone, the midpoint and the stop end of the runway feed live RVR readings to air traffic control.

CAT IIIB, the lowest category in routine use at Indian airports, can permit a landing in visibility that would send a CAT I flight elsewhere. CAT IIIC, which assumes no visibility at all, is not used operationally anywhere. The precise decision height and RVR figures for each category are published on the approach charts for a specific runway and vary with the airline’s approval, so treat any single number you read online as indicative rather than universal.

Why do both the aircraft and the pilots need CAT III approval?

Because a low visibility landing is a system, not a single piece of equipment, and every link has to be certified. Four things must line up at the same time.

• The runway and airport: a CAT III standard ILS, high intensity approach and centreline lighting, RVR sensors, protected ILS sensitive areas and published low visibility procedures.
• The aircraft: the required redundancy, typically multiple autopilots and radio altimeters, with autoland and rollout guidance certified for the category.
• The airline: a specific operational approval from the DGCA for that category, on that aircraft type.
• The pilots: both crew members trained and current for CAT III, with recency maintained in the simulator.

Remove any one of those and the flight is limited to a higher minimum, usually CAT I. That is why two aircraft on the same approach in the same fog can get different outcomes: one lands, the other diverts. Following the severe fog disruption of the 2023-24 winter, the DGCA issued instructions to airlines on fog season handling, including rostering appropriately qualified crews on flights to fog-prone airports and keeping passengers properly informed instead of holding them indefinitely.

Why does a CAT III airport still cancel flights in fog?

Landing is only one part of the operation. A CAT III capable airport can keep accepting arrivals and still lose most of its schedule, for reasons that have nothing to do with the ILS.

• Departures have their own minima. Take-off in low visibility is governed by separate limits and separate approvals, and the aircraft still has to be pushed back and taxied across an airfield the crew can barely see.
• Low visibility procedures cut capacity. When LVP are in force, spacing between aircraft increases to protect the ILS sensitive areas, taxi speeds drop and ground movements are tightly controlled. An airport that normally handles a full arrival rate may manage only a fraction of it.
• The other end matters. Your Delhi flight may be waiting on an aircraft that cannot depart a smaller airport with no CAT III infrastructure at all.
• Rotations collapse. A single narrowbody flies several sectors a day. One long morning hold puts that aircraft, and its crew, out of position for the rest of the day.
• Crew duty limits. Flight duty time limitations set by the DGCA are hard stops. A crew that times out cannot simply carry on once the fog lifts.

What happens to your ticket when a Delhi flight is fogged out?

If the flight is cancelled, DGCA rules on delays and cancellations generally give you a choice between a full refund and a seat on an alternate flight at no extra cost. Weather sits within the extraordinary circumstances carve-out, so cash compensation is usually not payable, but the refund or re-accommodation obligation still stands. Airlines are also expected to look after passengers during long airport delays.

Practically, the fastest route is the airline’s app or website rather than the airport queue. Check your PNR status before leaving home, because a flight showing a rolling delay can become a cancellation while you are on the road. If you booked through an agent or an online travel platform, the refund normally flows back through the channel you paid.

How do you plan around the Delhi fog season?

Dense fog in the Indo-Gangetic plain typically peaks from late December through January, with the worst visibility in the small hours and the first half of the morning. It usually improves as the sun burns through, though on the worst days it does not lift much at all.

A few habits help. Book late morning or midday departures during peak fog weeks. Avoid tight same-day connections through Delhi, particularly if the onward leg is a separate ticket, since a missed self-transfer is your cost, not the airline’s. Keep a buffer day before anything unmissable such as an international connection or a wedding. Turn on airline app notifications, and consider a fare that allows changes if your dates are fixed but your flight is not.

Common Questions

Does CAT III mean the aircraft lands itself?

Usually the autopilot flies the approach and the autoland system touches down and tracks the centreline during rollout, with the crew monitoring closely and ready to take over or go around. It is an approved, practised procedure rather than the aircraft being left to its own devices.

Is Delhi airport CAT III capable?

Yes, Delhi has CAT III capability, and the airport operator has upgraded runways for low visibility operations over the years. Which runways are available at any given time can change during maintenance or upgrade work, so check the airport operator’s advisories during the fog season.

Why did my flight get cancelled when others were landing?

Different aircraft, crews and airlines hold different approvals, and arrivals are treated separately from departures. A runway that is accepting CAT III arrivals can still be unusable for your departure if take-off minima are not met or if your aircraft never arrived from its previous sector.

What is runway visual range?

RVR is the distance a pilot can expect to see along the runway, measured by instruments beside it rather than estimated by eye. It is reported in metres for the touchdown, mid and stop-end sections, and it is the figure crews compare against their published minima.

Can I claim compensation for a fog cancellation?

Cash compensation is generally not payable because weather falls under extraordinary circumstances in the DGCA framework. You can still ask for a full refund or a free alternate flight, and for the care obligations that apply during long delays at the airport.

Are trains a better option during peak fog?

Not automatically. Dense fog also slows north Indian rail services, and long-distance trains frequently run late in the same conditions. If your travel is time-critical, building slack into the plan matters more than the mode you pick.

Rules, approvals and fees change: verify current specifics with the airline, the DGCA, or the airport before you travel.