VFR / IFR Minimums Checker

Basic VFR weather minimums in FAA-governed controlled airspace (Classes B, C, D, and E below 10,000 ft MSL) require 3 statute miles flight visibility and cloud clearances of 500 ft below, 1,000 ft above, and 2,000 ft horizontal from clouds. In Class B airspace, the requirement is reduced to 3 SM visibility with clear of clouds only — no specific vertical or horizontal cloud separation is required because Class B is a positive control environment where ATC provides separation for all aircraft. In Class E airspace at or above 10,000 ft MSL, minimums increase to 5 SM visibility and 1 SM horizontal, 1,000 ft above, and 1,000 ft below clouds. ICAO standard airspace minimums differ slightly from FAA and UK CAA minimums, so pilots operating internationally must verify local regulations.

Class G (uncontrolled) airspace has the most variable VFR minimums. During the day, at or below 1,200 ft AGL, the FAA requires only 1 statute mile visibility and clear of clouds — a very permissive standard designed to accommodate low-level agricultural and local flying. At night in Class G below 1,200 ft AGL, minimums increase to 3 SM and 500 ft below, 1,000 ft above, 2,000 ft horizontal. Above 1,200 ft AGL but below 10,000 ft MSL: 1 SM day, 3 SM night, with 500-1,000-2,000 cloud separation. At or above 10,000 ft MSL, Class G matches Class E high-altitude minimums: 5 SM and 1,000-1,000-1 SM cloud separation. These minimums represent absolute legal floors, not operational safety recommendations — many instructors recommend always applying Class E minimums as a conservative baseline.

These four categories describe the flight conditions at an airport or along a route. VFR (Visual Flight Rules): ceiling above 3,000 ft AGL AND visibility above 5 SM. No restriction on VFR flight in terms of weather. MVFR (Marginal VFR): ceiling 1,000–3,000 ft AGL AND/OR visibility 3–5 SM. Legal for VFR flight but marginal — a deterioration could result in inadvertent IMC. IFR (Instrument Flight Rules): ceiling 500–999 ft AGL AND/OR visibility 1–3 SM. VFR flight is not possible; IFR ratings, instrument-equipped aircraft, and ATC services are required. LIFR (Low IFR): ceiling below 500 ft AGL AND/OR visibility below 1 SM. Conditions below most instrument approach minimums. Even some IFR approaches cannot be flown legally under LIFR conditions. The boundaries between these categories are used by aviation weather services for PIREPs, METARs, TAFs, and graphics.

Special VFR (SVFR) is a clearance that allows a VFR aircraft to operate in a control zone (typically Class D or C airspace around an airport) in weather below basic VFR minimums, provided the aircraft remains clear of clouds and maintains at least 1 SM flight visibility. The pilot must request SVFR from ATC, and ATC must be able to provide separation from IFR traffic. At night, SVFR requires the pilot to be instrument-rated and the aircraft to be equipped for IFR flight. SVFR cannot be used in Class A or B airspace, is not available at some busy airports during IFR conditions, and does not override the cloud clearance and visibility requirements outside the control zone. Many pilots use SVFR to depart or arrive at a local airport when morning fog or low cloud has reduced visibility temporarily below basic VFR minimums.

Under FAA regulations (14 CFR 91.169), when a destination airport requires an alternate in the flight plan, the alternate airport must have weather forecasts at the ETA (plus or minus 1 hour) meeting specific minimums. For an airport with a precision instrument approach (ILS), the alternate minimum is a ceiling of 600 ft and visibility of 2 SM. For an airport with only a non-precision approach (VOR, NDB, LOC), the alternate minimum is 800 ft ceiling and 2 SM visibility. For an airport with no instrument approach procedure, weather must allow descent from the MEA under basic VFR conditions. These are standard alternate minimums — operators and commercial carriers often file higher alternate minimums depending on aircraft equipment, approach aids, and company operations specifications. Always check for published non-standard alternate minimums on approach charts.

The 1-2-3 rule is a FAA memory aid for determining when a destination alternate airport is required on an IFR flight plan. An alternate is required when, during the period from 1 hour before to 1 hour after the planned ETA at the destination, the weather forecast shows a ceiling less than 2,000 ft OR visibility less than 3 statute miles. If the forecast is better than 2,000 ft ceiling and 3 SM visibility throughout the 1-hour window, no alternate is legally required (under FAR Part 91). Note that this is a legal minimum — operationally it is prudent to always plan an alternate unless the destination forecast is confidently above minimums. Additionally, the "1-2-3 rule" does not apply to commercial operations under Parts 121 and 135, which have separate and generally stricter alternate requirements.

An ILS (Instrument Landing System) is a precision approach with both lateral (localiser) and vertical (glideslope) guidance. The standard ILS minimums depend on the category of approach. Category I (CAT I) ILS: Decision Altitude (DA) of 200 ft HAT and Runway Visual Range (RVR) of 1,800 ft (approximately ½ SM visibility) — the most common ILS in general aviation. Category II (CAT II) ILS: DA 100 ft and RVR 1,200 ft — requires special aircraft certification, special pilot training, and airport certification. Category IIIa ILS: DA below 100 ft (or no DA) and RVR 700 ft — requires autoland capability. Category IIIb: DA below 50 ft and RVR 150–700 ft. Category IIIc: zero-zero operation. CAT II and III approaches require specific aircraft equipment (autoland or HUD), recency requirements for both flight crew members, and specially certified runways.

EASA (and UK CAA post-Brexit) VFR minimums follow ICAO Annex 2 standards with some national variations. In Class A airspace, no VFR is permitted — IFR only. In Class B, C, D, and E airspace (controlled), the ICAO standard is 5 km flight visibility and clear of clouds plus 1,500 m horizontal, 1,000 ft above, and 300 m (1,000 ft) below clouds above 3,000 ft AMSL. Below 3,000 ft AMSL or 1,000 ft AGL, whichever is higher: 5 km visibility and 1,500 m horizontal, 1,000 ft above, 300 m below clouds. The UK additionally recognises a "clear of clouds" exemption in Class G airspace for helicopters below 3,000 ft in specific conditions. Note that the UK uses kilometres for visibility in regulations (5 km, 1.5 km) while FAA uses statute miles — always verify which unit system applies.

In FAA Class B airspace, the cloud clearance requirement is simply "clear of clouds" — meaning the aircraft must not be flying in a cloud. There is no requirement for a specific vertical separation above, below, or horizontal distance from clouds. This is because Class B airspace is a mandatory positive control environment where ATC must provide separation between all aircraft (VFR and IFR alike). The ATC radar provides the separation function that cloud clearance requirements normally serve in other airspace classes. In practice, "clear of clouds" means the pilot can see and avoid clouds — flying at the edge of a cloud layer within Class B is permissible provided ATC has been informed and separation from IFR traffic is being provided. Always remember that even within Class B, aircraft must be visible and the pilot must maintain positive visual contact with the aircraft's position relative to clouds.

No — FAA night VFR minimums are equal to or stricter than day minimums, never lower. In Class G airspace below 1,200 ft AGL, the day minimum is 1 SM clear of clouds. At night, this rises to 3 SM with standard cloud separation (500-1,000-2,000). In Class G above 1,200 ft AGL, day minimums are 1 SM (below 10,000 ft), while night is 3 SM. The rationale is straightforward: at night, the horizon is less distinct, unlighted terrain and obstacles are invisible, and the visual cues available to judge cloud proximity are severely reduced. Night VFR is significantly more demanding than day VFR and accident statistics reflect this — night VMC accidents often involve inadvertent entry into IMC or controlled flight into terrain (CFIT) because the visual environment that VFR relies on is severely degraded.