There is no consolidated public matrix of Asia-Pacific runway approach categories. The thresholds that define CAT I, CAT II and CAT III are published, but the airport-by-airport certification data is not — many states never filed it.
Hong Kong International Airport is the one documented exception, with public detail on when and how its runways operate in fog. That single row shows what the missing matrix would look like, and why you cannot find it anywhere else.
Two fog-bound flights, two airports barely fifty kilometers apart. One touches down on schedule while the other diverts to clear skies two hours away. Nothing about the aircraft or the crew explains the split — the difference is the runway itself, specifically its published approach category.
That is the hidden variable behind most fog-season disruption in Asia-Pacific: whether a runway is certified for CAT I, CAT II or CAT III operations. The framework is public; the airport-by-airport map is not.
Many states across the region never published aerodrome certification data in their national Aeronautical Information Publications, despite the International Civil Aviation Organization (ICAO) requiring it.
This article translates the categories first, then shows why the consolidated matrix does not exist, then walks through Hong Kong International Airport as the one documented row. That row matters because it proves the comparison is possible — the rest of the region just has not published its side.
What CAT I, II and III actually permit
The instrument landing system lets a crew descend through cloud and fog to a published decision height, then either land or go around. Two variables decide how low that descent can legally go: the decision height itself and the runway visual range. The latter is the distance a pilot can actually see down the runway from the flight deck.
At CAT I, the floor is the least forgiving of the three. The decision height bottoms out at 60 meters, and visibility must reach at least 800 meters — or 550 meters of runway visual range.
CAT II pushes that decision height down to between 30 and 60 meters, paired with runway visual range of at least 300 meters.
CAT III removes the visual reference almost entirely. Runway visual range sits below 300 meters, and the decision height is either below 30 meters or simply does not exist.
A CAT III-capable aircraft can touch down with essentially nothing on the windshield but instrument symbology — provided the runway is certified for it and the crew is qualified.
That certification clause is the part most passengers have never heard about.
Why the Asia-Pacific matrix you’d expect doesn’t exist
You would think the data is sitting in a single public file. It is not.
ICAO requires every state to publish the certification status of its aerodromes in the national AIP. Pilots brief from that document before every flight. Across much of Asia-Pacific, the relevant entry was simply never filled in.
What does exist sits in non-standardized technical sections that change name and structure from one country to the next. A researcher who knows where to look will find fragments in places like the AD 1.5 series of the AIP — a section few passengers, and not many travel journalists, have ever opened.
Even the runway classes themselves split into three bands — non-instrument, non-precision and precision — and are told apart in technical records by aeronautical charts and ICAO location indicators. That coding is built for flight planners, not for a traveler wondering whether a fog-delayed connection will push back.
So the missing matrix is not a research oversight; it is a publication gap that airlines and airports have lived with for years.
Ask a dispatcher why a fog-season buffer exists and you will get a shrug. Ask for a published CAT category at many regional airports and you will get silence.
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Hong Kong: the one published row
If the full matrix existed, each row would look like the one Hong Kong International Airport has already published.
That is the value of the Hong Kong example: it shows what the rest of the region could disclose because one airport already does. At HKIA, two triggers activate Low Visibility Procedures: visibility dropping below 550 meters, or a cloud base below 200 feet.
When either trips, the airfield shifts into a choreographed low-visibility routine rather than improvising one.
HKIA installed specialized centerline lead-off lighting on the runway exit taxiways, positioned to steer aircraft through the ILS-sensitive area when visibility is low. That is the kind of operational specificity a matrix row should carry — not just “ILS installed,” but what the airport does once fog actually closes in.
That 550-meter trigger is worth a second look because it mirrors the CAT I visibility floor from the same rulebook — the kind of cross-reference a published matrix would make explicit.
Most Asia-Pacific airports publish nothing close to this. Hong Kong’s row, single as it is, proves the comparison is possible — and makes the silence from the rest of the region harder to excuse.
What a runway has to prove before it earns CAT III
The category printed on a chart is not granted by paperwork alone. Under ICAO’s design manuals, certifying a runway for low-visibility approaches rests on three physical requirements: high-intensity lighting, cleared obstacle-free zones, and specialized ground-based navigation aids. Miss any one and the category drops, no matter how modern the terminal or how new the tower.
That is the piece most passengers never see. The lighting gives the crew a visual cue, the cleared zone removes obstacles, and the navigation aids hold the aircraft on the correct path. In dense fog, the margin between a successful landing and a go-around is a few hundred meters of lighting and a clean approach.
A CAT III-certified aircraft cannot use that capability if the runway itself is only CAT I. The legal operating floor belongs to the pavement and its infrastructure, not to the autopilot.
That is the distinction the missing matrix was supposed to make visible.
How to plan around the publication gap
For a traveler flying into Asia-Pacific during fog season, the practical lesson is less about memorizing categories and more about reading silence. If a hub airport does not publish runway certification data, its airline cannot give you a firm answer on fog-day performance. Not because the answer is secret, but because the official record was never produced.
That changes how to judge a tight connection. A 45-minute transfer at a hub with published low-visibility procedures is a different risk from the same transfer at an airport that publishes nothing. Build extra buffer into winter and monsoon-season itineraries that route through known fog-prone hubs.
Treat vague airline language about fog contingency as a signal that the underlying data may not exist, rather than that the airline is being evasive. The publication gap is the difference between a diversion and an on-time arrival — and for a connecting passenger, between making the next flight and sleeping in a terminal.
Key terms
- Decision height
- The altitude at which a pilot must abort the approach if the runway is not in sight. It is the floor for every instrument approach, set by the runway’s certification category. In this article, decision height is the number that separates CAT I, CAT II and CAT III — and the one most Asia-Pacific airports have never published.
- Runway visual range
- The distance a pilot can see down the runway from the flight deck, measured in meters. It is the second variable in every approach category, working alongside decision height to set the legal minimums. Hong Kong’s low-visibility procedures trigger at 550 meters of runway visual range, the same floor as CAT I.
- AIP
- Aeronautical Information Publication, the official document every state must maintain for its airspace and airports. Pilots brief from it before every flight, and ICAO requires aerodrome certification data to appear in it. Across much of Asia-Pacific, the relevant entries were never filled in.
- ILS-sensitive area
- The protected zone around an instrument landing system’s antennas where vehicles and aircraft can distort the signal. During low-visibility operations, airports must keep this area clear to preserve guidance accuracy. HKIA installed lead-off lighting specifically to steer aircraft through this zone when fog closes in.
