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Why Are There Mandatory Cloud Clearance Requirements?

Have you ever wondered why we have VFR weather minimums? Imagine you're skimming a cloud bank and another aircraft suddenly shoots out of the cloud right in front of you...

Why Cloud Separation Matters

Cloud clearance regulations all come down to ATC coverage, speed, and altitude. In flight training, students are rarely taught WHY there are so many airspace variations. IFR traffic is controlled by ATC, so weather and speed restrictions make sure that IFR and VFR aircraft can see and avoid each other.

It's an easy temptation for VFR pilots to fly through or around thin cloud layers, and it's rare for pilots to get busted by the FAA for breaking cloud clearance requirements. After all, there's no such thing as sky police on the lookout for you.

Requirements Vary Across Airspace Boundaries

Class B, C, D, E, and G airspace segments all have different weather minimums in the United States. In an effort to allow pilots flexibility while flying in different speed, altitude, and ATC environments, there are quite a few regulations you need to memorize.

They're complex segments of airspace, making it difficult to cite every single cloud clearance and visibility requirement from memory.

Class B Airspace Is Surprisingly Lenient

Class B airspace has some of the most strict equipment and communication requirements of any airspace. It surrounds the busiest airports in the country. But, it's got some of the most lax weather minimums. Why? Air Traffic Control. When you fly into Class B airspace you only need to stay clear of clouds with 3SM of visibility, day or night.

Air Traffic Control makes Class B airspace possible by constantly monitoring and separating each flight in the airspace, VFR or IFR. Approach and departure control transitions aircraft into and out of the airspace, and tower controllers sequence them in for landing and takeoff. Even if you're VFR, each airplane is being controlled and monitored.

Class C, D, E: Relatively Strict Requirements

Class C, D, and E airspace mimic each other in terms of VFR weather minimums (below 10,000' MSL). Unlike Class B, they have increased cloud clearance requirements due to a potential lack of ATC radar control. When you fly into a Class C or D airport under VFR, ATC is not required to keep you adequately separated from other VFR aircraft. Because of this, and the high density of traffic nearby, you need to stay further away from clouds so you can keep clear of traffic conflicts.

In Class E, IFR aircraft are controlled by ATC. This might be a center facility (Air Route Traffic Control Center) or approach/departure facility. As a VFR aircraft, you're on your own, but IFR aircraft must operate on an ATC clearance. That means the airspace is still controlled. That's why you have the same cloud clearance requirements as Class C or D airspace (below 10,000' MSL).

Class G Is The Most Lenient, And Confusing

Depending on how high you fly, and the time of day within Class G airspace, your visibility requirement could range anywhere from 1SM to 5SM. Cloud clearances range from "clear of clouds" to "1SM." There are 6 sets of Class G weather minimums associated with various altitudes during the day or night.

Need help understanding Class G airspace? Check out our Class G Airspace Article.

High Altitudes Increase Cloud Clearance Requirements

So why is there a difference in weather minimums at different altitudes? Starting at 10,000' MSL, you can fly faster than 250 knots. Accordingly, you'll need more visibility and distance from the clouds to see and avoid other aircraft. High speeds increase closure rates, so you'll have less time to react to oncoming traffic.

If you're flying in Class E or G airspace, your visibility requirement above 10,000' MSL is 5SM, day or night. You'll also need to stay 1SM horizontally from, 1,000' above, and 1,000' below clouds.

VFR weather minimums are there for your safety, and the safety of every other pilot and passenger flying. Staying well clear of clouds will give you the most time to react to a surprise traffic conflict.

Looking For More Info?

Want to learn more about airspace? Try our National Airspace System online course. With tons of quizzes and simple explanations, it's an easy way to get ready for your next checkride or flight review.


Swayne Martin

Swayne is an editor at Boldmethod, certified flight instructor, and commercial pilot for Mokulele Airlines. In addition to multi-engine and instrument ratings, he holds a PIC Type Rating for Cessna Citation Jets (CE-525). He graduated as an aviation major from the University of North Dakota in 2018. He's the author of the articles, quizzes and lists you love to read every week. You can reach Swayne at swayne@boldmethod.com, and follow his flying adventures at http://www.swaynemartin.com.

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