FAR Ninety-One Point One Fifty-Five, the VFR Weather Minimums, and the Three-Cornered Cloud Clearance Rule Every Pilot Memorizes and Half of Them Get Backwards

Under FAR 91.155, whether you’re legal to fly VFR depends on three things: your visibility, your distance from clouds, and the airspace you’re in. In the most common flying environment - controlled airspace below 10,000 feet during the day - you need 3 statute miles of visibility and cloud clearances of 1,000 feet above, 500 feet below, and 2,000 feet horizontal (the “3-152” rule). Those numbers loosen down low in uncontrolled airspace and tighten up high, but the logic never changes.

Why Do VFR Weather Minimums Exist?

When you fly under Visual Flight Rules (VFR), you are personally responsible for spotting other traffic and staying away from it. This is the principle of see and avoid - nobody is separating you from that other airplane but your own eyes.

Meanwhile, a whole other category of traffic is flying on Instrument Flight Rules (IFR): airliners, business jets, and general aviation pilots shooting approaches in the clouds. Those aircraft punch in and out of cloud layers constantly, descending through decks and popping out of the bottoms.

Picture a cloud as a wall you can’t see through. On the other side, closing at a couple hundred knots, could be a jet you’ll never see coming.

The cloud clearance rules exist to give you enough clear air that when a Boeing or a King Air comes out of that cloud, you both have a fighting chance to see each other and react. Visibility lets you see. Distance from clouds gives you time to act. Every value in the regulation flows from those two ideas.

What Is the 3-152 Rule?

The number most pilots remember is “3-152” because it applies to the largest chunk of everyday flying.

That breaks down as:

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

This applies in controlled airspace - Class E, and the Class C and Class D around airports - during the day, below 10,000 feet MSL. That’s most of the flying most pilots do, which makes it your bread-and-butter number.

Why Is It 1,000 Feet Above but Only 500 Below?

Students always ask this, and it’s a fair question. Think about who is coming out of that cloud and where they’re going.

An aircraft descending out of the bottom of a cloud on an approach is heading down, dropping through the altitude just below the cloud base. The rule keeps you a full 1,000 feet clear above because that’s where the descending traffic is punching through.

Sitting 500 feet below the base, combined with the geometry of an aircraft breaking out and leveling off, gives everyone a cushion. The numbers above and below aren’t the same, and they aren’t random.

What Are the VFR Minimums in Class G (Uncontrolled) Airspace?

Class G - uncontrolled airspace - hugs the ground out in the countryside, away from towers and radar. There’s less fast traffic and less IFR activity down low, so the FAA relaxes the rules. But relaxed doesn’t mean gone.

During the day in Class G, at or below 1,200 feet AGL, you need 1 statute mile of visibility and you must remain clear of clouds. That’s it - one mile and clear of clouds.

Clear of clouds means exactly that: not 500 below, not 2,000 across - just don’t fly into one. You can legally be right up underneath it.

Is Legal the Same as Safe?

No. This is where the instructor hat goes on.

One mile of visibility, scud running under a low deck, clear of clouds by a few feet, is perfectly legal in Class G in daytime. It is also exactly the picture that shows up in accident reports - VFR into instrument conditions, controlled flight into terrain, the pilot who pressed on under a lowering ceiling.

The regulation gives you permission, not a guarantee. The regs are a floor, not a target. Just because you can does not mean the day is telling you that you should.

How Do the Class G Rules Change at Night?

At night, Class G tightens up. At or below 1,200 feet AGL at night, visibility jumps to 3 miles, and the cloud clearances return: 1,000 above, 500 below, and 2,000 horizontal - that same 3-152 picture.

Why the change? Because at night you can’t see the clouds. In the dark, a wall of cloud is invisible until you’re in it, and by then your instruments are the only truth you have left. The rules get stricter precisely because your eyeballs - the whole basis of see and avoid - just got far less reliable.

There is one narrow exception: within half a mile of the runway in the traffic pattern at a Class G airport at night, you can drop to 1 mile and clear of clouds so you can actually get in and land. But keep the big picture - night in Class G means think 3 miles with the cloud clearances back in play.

What Are the VFR Minimums Above 10,000 Feet?

This is the one pilots forget entirely. Above 10,000 feet MSL and more than 1,200 feet AGL in controlled airspace, visibility goes up to 5 statute miles, and cloud clearance becomes 1,000 feet above, 1,000 feet below, and 1 statute mile horizontal.

Why so much bigger? Speed. Below 10,000 feet, the 250-knot speed limit protects everyone. Above 10,000, that limit comes off and aircraft can move much faster. A mile of horizontal clearance isn’t overkill when combined closure speeds hit five or six hundred knots - a mile disappears in seconds. More closure speed, more room required.

A Simple Mental Model to Remember All of It

The higher and faster the surrounding traffic is likely to be, the more room the rules give you. That produces a clean ladder:

• 1 mile and clear of clouds - low in Class G by day
• 3-152 (3 miles; 1,000 above / 500 below / 2,000 horizontal) - the main body of controlled airspace
• 5 miles; 1,000 above / 1,000 below / 1 mile horizontal - up high above 10,000 feet

How Will This Show Up on My Checkride?

If you’re training, this is coming for you. The Airman Certification Standards (ACS) list knowledge of VFR weather minimums under preflight and cross-country planning, and the examiner grades you against that document.

Expect the examiner to pull up current conditions or invent a scenario: here’s your ceiling, here’s your visibility, here’s the airspace you’re departing into - are you legal? Then, going a level deeper: are you comfortable? What’s your personal minimum here?

The examiner isn’t trying to trap you on whether it’s 500 below or 500 above. They want to know whether you understand that the sky is divided into layers with different rules, and whether you know which layer you’re in when you firewall the throttle.

How Do I Apply This When Planning a Cross-Country?

Don’t just check the weather - check the airspace you’ll fly through and match the minimums to it.

Departing a Class G airport and climbing into the Class E shelf that begins at 700 or 1,200 feet AGL? Your required minimums change the instant you cross that invisible line. You go from 1 mile and clear of clouds to 3-152 just by climbing.

Know where the floor of controlled airspace sits on your sectional - the magenta or blue shading - because that’s the altitude where your rules change. That’s the difference between a pilot who memorized a chart and one who understands the sky.

Worked Example: Are You Legal to Depart?

You’re at a nontowered field. Class E begins at the surface, or perhaps at 700 feet - you checked the chart. Ceiling is 2,000 broken, visibility 4 miles in haze.

Work it. You’re in controlled airspace, daytime, below 10,000 feet, so the standard is 3-152:

• Visibility: You need 3 miles. You have 4. Legal.
• Cloud clearance: You need to stay 500 feet below the clouds. Bases are at 2,000, and traffic pattern altitude is 1,000 - so you can fly the pattern a full 500 below the base. Legal.

So you are legal. But are you comfortable? Four miles in haze isn’t much. Haze flattens everything, kills your horizon, and hides traffic against a milky sky. That’s a day to stay close to home, fly the pattern, and keep your head on a swivel. The difference between legal and wise is doing all the talking.

The One-Sentence Version

FAR 91.155 tells you the line you cannot cross. Your judgment tells you how close to that line you’re willing to fly. The visibility number lets you see the traffic; the cloud clearance number gives you time to do something about it. Every value in the regulation is just those two ideas, scaled up or down depending on how fast the airplane you can’t see is going.

The full regulation is free to read in 14 CFR 91.155, and the FAA lays it out plainly in the Aeronautical Information Manual (AIM) and the Pilot’s Handbook of Aeronautical Knowledge (PHAK).

Key Takeaways

• 3-152 is your core number: 3 miles visibility, 1,000 above / 500 below / 2,000 horizontal in controlled airspace below 10,000 feet by day.
• Class G day (≤1,200 AGL) is the loosest: just 1 mile and clear of clouds - legal, but often not safe.
• Night and altitude tighten the rules: Class G at night reverts to 3-152; above 10,000 feet MSL it’s 5 miles and 1,000/1,000/1 mile.
• The rules scale with closure speed: more potential traffic speed means more required clearance.
• Match minimums to airspace before you fly: your required numbers change the instant you cross into controlled airspace.