Flight Categories Explained: VFR, MVFR, IFR and LIFR

Flight categories (VFR, MVFR, IFR and LIFR) sort the reported ceiling and visibility at an airport into four bands, from good to poor. Open almost any aviation weather map and the airports are dotted green, blue, red and purple: those colors are the categories. They are the fastest way to scan the weather across a region, and one of the easiest things to misread, because the names sound like regulations and they are not.

The four flight categories and their exact thresholds

The FAA defines the categories in AIM 7-1-7, Categorical Ceiling and Visibility Conditions, and the Aviation Weather Handbook (FAA-H-8083-28B) repeats them with the colors most weather sites use.

Thresholds from AIM 7-1-7 (Basic with Change 3, effective July 9, 2026); colors from FAA-H-8083-28B section 3.4.2.14.

The boundaries are not symmetrical, and that is where the mistakes live. A ceiling of exactly 3,000 feet is MVFR, not VFR, because VFR needs a ceiling greater than 3,000. Visibility of exactly 5 SM is MVFR for the same reason. Going the other way, exactly 1,000 feet and exactly 3 SM are still MVFR, since IFR starts below those values, and exactly 500 feet and exactly 1 SM are IFR, since LIFR starts below them. The rule of thumb: a boundary value belongs to the lower category. The VFR line is the only one it never reaches.

Whichever element is worse sets the category

The AIM's wording is "and/or" for MVFR, IFR and LIFR, and "and" for VFR: to be VFR, both the ceiling and the visibility have to qualify.

So a report of 10 SM visibility under a 700 ft overcast is IFR, because of the ceiling. A report of 2 SM in haze with only scattered clouds is also IFR, because of the visibility. The color on the map does not tell you which element caused it, so open the report.

What counts as a ceiling

Under 14 CFR 1.1, a ceiling is the height above the surface of the lowest layer of clouds or obscuring phenomena reported as broken, overcast or obscuration, and not classified as thin or partial. In report terms:

• BKN (broken, 5 to 7 oktas) and OVC (overcast, 8 oktas) are ceilings.
• VV (vertical visibility into an obscured sky) is a ceiling. VV003 is a 300-foot ceiling.
• FEW and SCT are not ceilings, no matter how low they are.
• SKC means no clouds. CLR (automated stations) means no clouds detected at or below 12,000 feet. Either way there is no ceiling to count.

Ceilings are heights above ground level in METARs and TAFs. A scattered layer at 400 feet does not change the category, even though it might matter a great deal to you on a night approach.

METAR KXYZ 031853Z 21008KT 10SM SCT008 BKN035 22/14 A3002

This example (composed for this article, not a real report) has clouds at 800 feet, but they are scattered, so the ceiling is the broken layer at 3,500 feet. With 10 SM, this is VFR. The scattered layer at 800 feet is a real consideration on the approach. It is not a ceiling.

Worked examples for each category

These are all composed for illustration. The station identifier KXYZ is a placeholder.

VFR

METAR KXYZ 031553Z 27010KT 10SM FEW045 SCT250 18/06 A3010

No broken or overcast layer, so there is no ceiling. Visibility 10 SM is greater than 5. Both elements qualify: VFR.

MVFR, sitting on both boundaries

METAR KXYZ 031253Z 16006KT 5SM BR BKN030 OVC060 14/12 A2998

Ceiling 3,000 feet (the lowest broken layer). That is MVFR, because VFR needs more than 3,000. Visibility 5 SM is also MVFR, because VFR needs more than 5. A rounding mistake on either value would paint this airport green.

IFR

METAR KXYZ 031053Z 09005KT 2SM -RA BR OVC008 12/11 A2985

Ceiling 800 feet is IFR (500 to less than 1,000). Visibility 2 SM is also IFR (1 to less than 3).

LIFR, from the ceiling alone

METAR KXYZ 030953Z 00000KT 10SM OVC004 11/10 A3001

Visibility is excellent, but the overcast at 400 feet is less than 500. Whichever is worse wins: LIFR.

LIFR in fog

METAR KXYZ 030853Z 00000KT 1/4SM FG VV002 09/09 A3003

Visibility one quarter mile, sky obscured with a vertical visibility of 200 feet (a 200-foot ceiling). Both are below the LIFR thresholds.

International reports in meters, 9999 and CAVOK

Outside the US, most stations report visibility in meters, and the US categories still work if you convert. One statute mile is 1,609 meters, so the boundaries fall at about 1,609 m (1 SM), 4,828 m (3 SM) and 8,047 m (5 SM). The commonly reported values 1,600 m, 4,800 m and 8,000 m each sit just below a boundary. Convert strictly and each one lands in the lower category.

9999 means a visibility of 10 kilometers or more, as Australia's Bureau of Meteorology puts it in its METAR/SPECI guide; the AIM's METAR key notes that reports outside the US give visibility as a four-digit value in meters. Ten kilometers is a little over 6 SM, so on its own 9999 is VFR visibility.

METAR EGXX 031150Z 24012KT 4000 BR BKN012 12/10 Q1012

In this example (a placeholder station, composed for illustration), 4,000 meters is about 2.5 SM, which is IFR visibility. The ceiling of 1,200 feet alone would be MVFR. The worse element wins: IFR.

CAVOK (ceiling and visibility OK) replaces the visibility, weather and cloud groups when four conditions hold at once (FAA-H-8083-28B section 27.4.2.6). Visibility is 10 km or more. There is no cloud below 5,000 feet (1,500 m) or below the highest minimum sector altitude, whichever is greater. There is no cumulonimbus, and no significant weather. Since it guarantees at least 10 km of visibility and no cloud below 5,000 feet, a CAVOK report is always VFR by the US category definitions.

Two cautions. CAVOK does not mean clear skies: there can be cloud above 5,000 feet, or above the sector altitude in mountainous terrain. And the NWS does not use CAVOK in US domestic TAFs, so you will only meet it in international reports and forecasts.

Watch the conversion near the boundaries. 8,000 meters is about 4.97 SM, which falls inside the MVFR visibility band if you convert strictly, even though it feels like plenty.

Why a flight category is not a VFR weather minimum

The categories are labels for situational awareness. The handbook says it plainly: the VFR flight category "is not to be confused with the basic VFR weather minimums given in 14 CFR § 91.155," and "there are no 14 CFR part 91 MVFR weather minimums" at all (FAA-H-8083-28B sections 3.4.2.14 and 3.4.2.15).

The rules are in 14 CFR 91.155, and they depend on the class of airspace, your altitude, and whether it is day or night. The full table by airspace class is its own post; three disagreements between the label and the rule show why the distinction matters.

An IFR-colored dot is not automatically illegal VFR. At an airport whose surface airspace is Class G, the daytime minimum for airplanes at or below 1,200 feet AGL is 1 SM and clear of clouds under 91.155(a), so a field reporting 2 SM under scattered clouds is IFR by category but not below the regulatory visibility there by day. If the airport has a surface area, 91.155(d) requires 3 SM, and at night in Class G the minimum is 3 SM outside the traffic-pattern exception in 91.155(b)(2).

The surface-area rules do line up with the IFR boundary. Within the surface area of Class B, C, D or E airspace, 91.155(c) prohibits VFR beneath a ceiling of less than 1,000 feet, and 91.155(d) requires ground visibility of at least 3 SM to take off, land or enter the traffic pattern, unless you hold a special VFR clearance under 91.157. The numbers match. The category is still a label and the regulation is still the rule.

A green dot can still be illegal or unsafe. Cloud clearance (500 feet below, 1,000 feet above and 2,000 feet horizontal in Class C, D and E airspace below 10,000 feet MSL) is not part of the category at all. Neither are terrain, freezing levels, convection or wind.

How to use flight categories well

Categories are at their best as a scanning tool. A map where the green stops two-thirds of the way along your route tells you, in a glance, where to spend your briefing time.

Open the report behind every non-green dot on your route and find out whether it is the ceiling or the visibility, and whether it is improving or worsening across recent observations. Where a tool colors TAF periods the same way, read those too; they show whether the destination is expected to go IFR around your arrival. Do the arithmetic yourself on boundary values, because 3,000 feet, 5 SM, 1,000 feet and 3 SM are all MVFR, not the category above them. And compare against your own minimums, not the color. A low-time pilot's personal minimums usually sit well above the MVFR line.

The aviationweather.gov METAR page shows official observations. How to read a METAR decodes the observation group by group, and How to read a TAF does the same for the forecast.

This article is educational and is not a substitute for the current regulations, the AIM, official weather briefings, or instruction from a CFI. Check the current text at the linked sources before you rely on any detail.