What Are Flight Categories?
Flight categories are standardized classifications that describe the current weather conditions at an airport based on visibility and cloud ceiling. These categories help pilots quickly assess whether they can fly under Visual Flight Rules (VFR) or need to use Instrument Flight Rules (IFR).
The four categories are used throughout aviation weather products, including:
- METAR reports and airport weather displays
- Aviation weather maps and charts
- Flight planning applications
- ATC communications and pilot briefings
Understanding these categories is essential for every pilot, regardless of rating or experience level. They form the foundation of go/no-go decision making.
Detailed Category Breakdown
V VFR - Visual Flight Rules
Ceiling Requirement:
Greater than 3,000 feet AGL
Visibility Requirement:
Greater than 5 statute miles
VFR conditions represent ideal flying weather. Pilots can clearly see and avoid terrain, traffic, and obstacles. Most general aviation flights occur in VFR conditions.
What it means for pilots:
- Student pilots and private pilots can fly freely
- No instrument rating or IFR flight plan required
- Visual navigation using ground references is easy
- Good conditions for training and recreational flying
M MVFR - Marginal Visual Flight Rules
Ceiling Requirement:
1,000 to 3,000 feet AGL
Visibility Requirement:
3 to 5 statute miles
MVFR conditions are legal for VFR flight but require extra caution. These conditions often transition to IFR, and pilots should have an "out" planned.
What it means for pilots:
- VFR flight is legal but challenging
- Reduced margins for error
- Conditions may deteriorate rapidly
- Consider postponing if you're a low-time pilot
- Have alternate airports identified
Safety Note: Many VFR-into-IMC accidents begin in MVFR conditions that worsen unexpectedly. If you're uncomfortable with MVFR, wait for better weather.
I IFR - Instrument Flight Rules
Ceiling Requirement:
500 to 999 feet AGL
Visibility Requirement:
1 to less than 3 statute miles
IFR conditions require pilots to fly by reference to instruments rather than visual cues. Only pilots with an instrument rating, in properly equipped aircraft, with an IFR flight plan can legally fly in these conditions.
Requirements for IFR flight:
- Current instrument rating
- IFR-equipped aircraft
- Filed and activated IFR flight plan
- ATC clearance
- Currency requirements met (6 approaches, holds, tracking in past 6 months)
Warning: VFR pilots must NOT attempt to fly in IFR conditions. VFR-into-IMC is a leading cause of fatal general aviation accidents. The average life expectancy of a VFR pilot who enters IMC is approximately 178 seconds.
L LIFR - Low Instrument Flight Rules
Ceiling Requirement:
Below 500 feet AGL
Visibility Requirement:
Less than 1 statute mile
LIFR represents the most challenging instrument conditions. Even experienced instrument pilots treat LIFR with great respect. Many airports have approach minimums higher than LIFR conditions allow.
Considerations for LIFR:
- Many non-precision approaches have minimums above LIFR
- Only precision approaches (ILS, LPV) may be usable
- Alternate airports may also be LIFR
- Significant decision-making required
- Even airlines may delay or divert in LIFR
Determining Flight Category
Flight category is determined by whichever value is worse - ceiling OR visibility. Here's a decision flowchart:
| Category | Ceiling | AND/OR | Visibility |
|---|---|---|---|
| VFR | > 3,000 ft AGL | AND | > 5 SM |
| MVFR | 1,000 - 3,000 ft AGL | OR | 3 - 5 SM |
| IFR | 500 - 999 ft AGL | OR | 1 - < 3 SM |
| LIFR | < 500 ft AGL | OR | < 1 SM |
Example Scenarios:
Ceiling: 5,000 ft | Visibility: 10 SM
→ VFR (both values exceed VFR minimums)
Ceiling: 2,500 ft | Visibility: 10 SM
→ MVFR (ceiling is between 1,000-3,000 ft)
Ceiling: 10,000 ft | Visibility: 2 SM
→ IFR (visibility is between 1-3 SM, overrides good ceiling)
Ceiling: 300 ft | Visibility: 1/2 SM
→ LIFR (both values are LIFR)
What Constitutes a Ceiling?
Not all cloud layers create a ceiling. A ceiling is defined as the lowest layer of:
- Broken (BKN) clouds - 5/8 to 7/8 sky coverage
- Overcast (OVC) clouds - complete sky coverage
- Vertical Visibility (VV) - when sky is obscured
These do NOT constitute a ceiling:
- Few (FEW) clouds - 1/8 to 2/8 coverage
- Scattered (SCT) clouds - 3/8 to 4/8 coverage
- Clear (CLR/SKC) - no clouds
Example:
SCT015 BKN040 OVC100
The ceiling is 4,000 feet (BKN040), not 1,500 feet. The scattered layer at 1,500 feet does not count as a ceiling.
Flight Category and Your Go/No-Go Decision
Flight categories are just one factor in your preflight decision. Consider:
- Your certification - Can you legally fly in these conditions?
- Your currency - When did you last fly in similar conditions?
- Your comfort level - Are you confident in your abilities?
- Forecast trends - Is weather improving or deteriorating?
- Alternatives - What if conditions worsen en route?
- Personal minimums - What are your self-imposed limits?
Pro Tip
Establish personal minimums that are higher than legal minimums. Many experienced pilots won't fly VFR in anything worse than high MVFR, regardless of their ratings.