VFR vs IFR Flight Categories Explained

Updated: 2026-09-08 · First published: 2026-04-03

Open any aviation weather map and airports are coloured green, blue, red and magenta. Those colours are flight categories: a four-step scale that condenses a METAR or TAF into one word — VFR, MVFR, IFR or LIFR — using nothing but the ceiling and the visibility. This guide gives the exact thresholds, shows how to derive the category from a raw report, and clears up the most common confusion of all: a flight category is not a flight rule.

The four categories

The rule that ties the table together: the worse element wins. Check the ceiling, check the visibility, take whichever lands in the lower category. VFR requires both to be VFR; any single value in a lower band pulls the whole report down to that band.

Where the ceiling comes from

The ceiling is the height of the lowest cloud layer reported as BKN (broken, 5–7 oktas) or OVC (overcast, 8 oktas), or the vertical visibility VV when the sky is obscured. FEW and SCT layers never form a ceiling, no matter how low they are: SCT004 BKN025 has a 2,500 ft ceiling, not 400 ft. Heights are in hundreds of feet above the aerodrome. If you are not yet comfortable with the cloud groups, read how to read a METAR first.

Where the visibility comes from

The prevailing visibility group: metres outside the United States (0800, 4000, 9999), statute miles inside it (1/2SM, 3SM, 10SM). The category thresholds were written in statute miles, so metric reports are converted: 1 SM ≈ 1,609 m, 3 SM ≈ 4,800 m, 5 SM ≈ 8,000 m. In practice, 9999 and CAVOK are VFR visibility; 4000 is MVFR; 2000 is IFR; 0800 is LIFR. Runway visual range (R24/…) is not used for the category.

Worked examples

Category versus rules

This is where most confusion lives. A flight category is a description of the weather. Flight rules are a legal regime: under VFR you navigate by outside reference and stay clear of cloud; under IFR you fly on instruments under ATC clearance. The two use the same letters but answer different questions.

• You may fly IFR in VFR weather — airlines do it every day.
• You may not assume you can fly VFR in MVFR weather. Legal VMC minima depend on airspace class (for example, Class G below 3,000 ft AMSL in many ICAO states needs only 5 km and clear of cloud in sight of the surface), your licence and the time of day. MVFR is a warning that VFR is becoming marginal, not a permission or a prohibition.
• An IFR or LIFR category means an instrument approach will be needed to land — and the numbers must be checked against the approach minima for the runway in use, not against the category thresholds.

Europe and NATO: colour states

Military and some European briefings use colour states instead, with tighter steps at the low end. They are also derived from ceiling and visibility, with the worse element governing:

Note that colour states use the lowest cloud layer of 3 oktas or more (SCT counts), unlike the US categories, so the same METAR can be BLU and MVFR at once. Read the scale the briefing actually uses.

Using categories in a TAF

A TAF is a sequence of periods, and each period has its own category. The trap is to read the headline group, see VFR, and stop. A forecast of 9999 SCT030 TEMPO 0300/0306 0800 FG BKN002 is VFR with a LIFR window between 03:00 and 06:00 UTC — exactly when an early departure would be planning to go. For alternates, most operators require the alternate to be forecast at or above a fixed margin over the approach minima for one hour either side of the ETA; the category gives you the first, fast screen before you open the approach plate.

Why the category matters even to instrument pilots

Because it is the quickest honest summary of an airport's weather, and because dispatch, ATC flow management and most weather maps speak this language. A glance at a region coloured red and magenta tells you where approaches will stack up and where alternates will be scarce. On METAR & TAF 3D the category is computed for every reporting airport from the live METAR and for each TAF period, and shown on the map and on every station page beside the raw report and the runway crosswind: LTFM Istanbul · LTAI Antalya · LTBS Dalaman · EGLL London Heathrow · EDDF Frankfurt · LFPG Paris CDG · EHAM Amsterdam · KJFK New York JFK · OMDB Dubai · LEMD Madrid. Browse the airport directory by country to check any field before you plan.

Frequently asked questions

Is the flight category the same as the flight rules I must fly under?

No. The category describes the weather at an aerodrome using fixed ceiling and visibility thresholds. Flight rules — VFR or IFR — are what you file and how you operate. You can legally fly IFR in VFR conditions; whether you can fly VFR in MVFR conditions depends on the airspace class and your licence, not on the category label.

Which counts when ceiling and visibility disagree?

The worse of the two. A 4,000 ft ceiling with 2 statute miles of visibility is IFR because the visibility is IFR, even though the ceiling alone would be VFR.

What ceiling is used if there are several cloud layers?

The lowest layer reported as BKN (broken) or OVC (overcast), or the vertical visibility (VV). FEW and SCT layers are ignored, however low they are.

Do the categories apply outside the United States?

The four-colour VFR/MVFR/IFR/LIFR scheme is a US National Weather Service convention, but it is used on aviation weather maps worldwide, including this one. Legal VMC minima in ICAO countries are set per airspace class and differ from these thresholds.

Where do the categories come from in a TAF?

From each forecast period. A TAF that reads VFR at issue but contains TEMPO 0800 FG BKN002 has a LIFR period, and that is the period that matters for planning an approach or an alternate.

Read next

• How to Read METAR Reports: A Pilot's Guide
• Airports by country — live METAR and TAF for every reporting station
• World weather rankings from the observation archive