FAR Ninety-One Point One Five Five, the Cloud Clearance Table Every Student Memorizes Wrong, and the Class Golf Night Rule That Surprises Pilots Who Should Know Better

FAR 91.155 is the regulation every student pilot memorizes for the written exam and then slowly lets drift. It governs two things: how far you must be able to see, and how far you must stay from clouds. Both answers change depending on what class of airspace you’re in, how high you are, and whether it’s day or night.

What Does FAR 91.155 Actually Regulate?

The regulation controls visibility, measured in statute miles, and cloud clearance, measured in feet vertically and feet or statute miles horizontally. These two variables determine whether you are legal to fly VFR in any given piece of airspace at any given moment.

The numbers change across six distinct scenarios: Class B, Class C and D, Class E at and below 10,000 feet MSL, all airspace above 10,000 feet MSL, Class G during the day, and Class G at night. Each has its own requirements.

What Are the VFR Minimums in Class B Airspace?

Class B airspace - the large, layered rings surrounding major airports - requires 3 statute miles of visibility and clear of clouds.

“Clear of clouds” does not mean the sky must be cloudless. It means you cannot be inside a cloud. The FAA does not assign a specific vertical or horizontal clearance number for Class B because radar coverage and active ATC separation already manage traffic within this airspace. Your job is to stay visual and out of the clouds.

What Are the VFR Minimums in Class C, D, and E Airspace?

Class C, Class D, and Class E airspace at and below 10,000 feet MSL all share identical minimums:

• 3 statute miles of visibility
• 500 feet below clouds
• 1,000 feet above clouds
• 2,000 feet horizontal from clouds

One way to lock in the cloud clearance numbers: scale by 100 - 5, 10, 20 - which gives you 500, 1,000, 2,000.

Recognize that you’ve learned one rule that applies to three classes of controlled airspace. You’re not memorizing three separate tables. The symmetry is deliberate and useful.

What Changes Above 10,000 Feet MSL?

Flying VFR above 10,000 feet MSL triggers significantly higher minimums:

• 5 statute miles of visibility
• 1,000 feet below clouds
• 1,000 feet above clouds
• 1 statute mile horizontal from clouds

The horizontal clearance jumps from 2,000 feet to a full statute mile. At higher altitudes, traffic moves faster - turbine aircraft cover substantially more ground per minute - so the required margins expand to give you adequate time to see and avoid.

What Are the Class G Daytime VFR Minimums?

Class G is uncontrolled airspace. No radar coverage, no radio requirement. It occupies the lowest altitudes, below the floor of the controlled airspace system. The FAA applies the most permissive minimums in the entire regulatory framework here, recognizing that daytime, low-altitude, slow flight requires less margin to maintain adequate see-and-avoid capability.

At or below 1,200 feet AGL in Class G airspace during the day:

• 1 statute mile of visibility
• Clear of clouds

The 1,200-foot AGL threshold is meaningful. It marks the approximate boundary between the low-and-slow environment and airspace where faster traffic begins to mix in.

Above 1,200 feet AGL but still in Class G airspace during the day, the minimums step up:

• 1 statute mile of visibility
• 500 feet below, 1,000 feet above, 2,000 feet horizontal

The cloud clearance numbers now match Class C, D, and E - but visibility remains at 1 statute mile rather than 3.

What Are the Class G Nighttime VFR Minimums - and Why Do They Surprise Pilots?

This is the combination that catches even experienced pilots off guard.

At night, below 1,200 feet AGL in Class G airspace, the one-mile/clear-of-clouds daytime minimums disappear entirely. The requirements jump to:

• 3 statute miles of visibility
• 500 feet below clouds
• 1,000 feet above clouds
• 2,000 feet horizontal

The nighttime Class G minimums match Class C, D, and E. Uncontrolled airspace at night carries the same visibility and cloud clearance requirements as controlled airspace.

The reasoning is straightforward. During the day with one mile of visibility, you can pick out a water tower, terrain shadows, or another aircraft. At night, a mile of visibility provides almost no useful information - you may not see an obstruction until it’s far too late. The FAA extended controlled airspace margins into nighttime Class G to compensate for the dramatic reduction in visual cues.

Many pilots know the daytime Class G numbers confidently and have never examined the night column carefully. That gap is exactly the kind of thing that can turn a legal departure into a dangerous one.

What Is Special VFR, and When Can You Use It?

Special VFR is a clearance you request from ATC to operate inside controlled airspace with less than standard VFR minimums. The minimums under Special VFR are:

• 1 statute mile of flight visibility
• Clear of clouds
• Visual contact with the surface must be maintained

Special VFR is not something you declare unilaterally. You request it; ATC grants it or they don’t - based on workload, traffic, and availability.

At night, Special VFR requires an instrument rating and an IFR-equipped aircraft. The FAA will not permit a pilot without instrument training to navigate through controlled airspace at night with one mile of visibility.

Special VFR is also explicitly prohibited at certain airports. Check the communications section of the Chart Supplement - “NO SVFR” is a regulatory prohibition, not a suggestion.

A typical use case: visibility is 2 statute miles, a broken layer sits at 800 feet, and you need to enter a Class D airport. That’s below the 3-mile VFR minimum. If you can maintain 1 mile of flight visibility and see the ground, you can request Special VFR. If the tower can accommodate you, you enter legally. It’s a legitimate tool, though not a routine one.

How Should You Practice This for the Checkride?

The Airman Certification Standards for the private pilot certificate require candidates to apply VFR weather minimums in context - not just recite a table. An examiner may present a scenario: here’s the altitude, here’s the airspace class, here’s the time of day. What are your minimums? They’re looking for reasoning, not retrieval.

An effective practice method: open a sectional chart, pick ten random locations, identify the airspace class, assign a time of day, and work through the minimums. Include Class G scenarios, nighttime scenarios, and altitudes above 10,000 MSL. Build comfort with the reasoning process so the logic becomes automatic.

Legal Minimums Are Not Safe Minimums

FAR 91.155 defines the legal floor - not the safety margin. One mile of visibility over flat terrain on a clear afternoon is a fundamentally different experience from one mile of visibility over unfamiliar terrain at 500 feet AGL with a ceiling that has been dropping for the past 30 minutes.

The accident record includes pilots who were technically legal right up until they weren’t. They departed with conditions below good VFR but above the regulatory minimums. As the flight progressed, conditions deteriorated. The margin they thought they had narrowed and disappeared.

FAA research on VFR into IMC accidents - cases where a VFR pilot enters clouds or low visibility and loses control - shows a consistent and sobering pattern. The average time from IMC entry to impact is approximately 178 seconds. Less than three minutes. That is not enough time for a pilot without instrument training to recognize what is happening, decide on a response, and execute a successful recovery.

Set personal minimums before you are in the cockpit facing deteriorating conditions. Write them down and attach them to your kneeboard or preflight checklist. A reasonable starting framework: no VFR departure with visibility below 5 statute miles and a ceiling below 2,000 feet until you have substantial experience and regular instrument practice. Adjust to your aircraft and experience level. The key is that the decision is made on the ground, when you’re thinking clearly - not when the temptation to press on is right in front of you.

The regulation draws the legal line. You draw your safety line well back from it.

Key Takeaways

• Class B: 3 miles visibility, clear of clouds
• Class C, D, and E (at/below 10,000 MSL): 3 miles visibility, 500 below / 1,000 above / 2,000 horizontal - one rule, three airspace classes
• Above 10,000 MSL: 5 miles visibility, 1,000 below / 1,000 above / 1 mile horizontal
• Class G daytime at/below 1,200 AGL: 1 mile visibility, clear of clouds - the most permissive minimums in the system
• Class G nighttime at/below 1,200 AGL: 3 miles visibility, 500 below / 1,000 above / 2,000 horizontal - identical to controlled airspace, and the number pilots most often miss
• Legal minimums are a floor, not a target; personal minimums should be set higher, in writing, before every flight