Cloud clearance

The rule, and what it buys you

Stay 500 feet below any cloud, or 2,000 feet out to the side of it, and keep at least 3 statute miles of visibility. That is the whole rule, and the numbers are not arbitrary. A manned aircraft can leave the base of a cloud at 150 knots with no way to see a small drone beneath it, and no way to be seen by you. At that speed a pilot covers about 250 feet every second. The buffers are not a measure of how big the cloud is; they are a purchase of time. They give a pilot who pops out of the gray a few seconds to notice something small, decide, and move, and they give you the same seconds to notice a wing coming and get out of the way.

14 CFR § 107.51(c), (d)

This lesson goes deeper than the operating-limits section of the Regulations chapter. Read that first if “500 and 2,000” is new; here the interest is in the edges: how the two distances combine, what happens above a cloud, and what the visibility number actually measures.

The geometry people get wrong

Read the regulation closely and you find two distances: 500 feet below the cloud, and 2,000 feet horizontally from the cloud. People often take that as a box you must be outside of in both directions at once, or as two separate requirements you have to satisfy together. The practical meaning is a keep-out zone. Picture the cloud, a skirt 500 feet deep hanging below its base, and an apron 2,000 feet wide around its sides. You may not be inside that volume. You can be legal by being far enough beneath it, or legal by being far enough to the side of it. One clearance is enough; you do not need both.

14 CFR § 107.51(d)(1)-(2)

Be careful about the wording, because the printed text joins the two items with “and”. It lists the two minimum distances the aircraft must keep from a cloud. The reading used by this site, the FAA’s own materials, and the test is the keep-out volume described above: a drone directly beneath a cloud at 600 feet below its base is plainly fine, even though it is zero feet to the side.

The numbers interact with another limit you already know. The altitude cap is 400 feet above ground level, so a cloud whose base is only 700 feet above the ground leaves you 300 feet of vertical clearance at maximum height. Under that cloud you must stay below 200 feet AGL, or move 2,000 feet away from the cloud’s edge. A ceiling of 900 feet AGL is the lowest base that lets you fly the full 400 feet while sitting directly underneath.

14 CFR § 107.51(b), (d)(1)

What about above a cloud?

The regulation’s text says nothing about “above”. Section 107.51(d) names only below and horizontal. But the Advisory Circular is explicit: the small unmanned aircraft cannot be operated above any cloud, and there cannot be obstructions to visibility, such as smoke or a cloud, between the aircraft and the remote pilot in command.

AC 107-2A ¶ 5.12.3

Think about what that is guarding. Visual line of sight means you keep the aircraft in view with your own eyes, unaided other than by corrective lenses. An aircraft on top of a cloud deck, or hidden behind a cloud, is by definition not in your view. So even where 107.51(d) is silent, the line-of-sight requirement stops you. The answer on the test is the same either way: flying above a cloud is not an option.

14 CFR § 107.31(a)

Flight visibility, as the rule defines it

“Visibility” in everyday speech means how far you can see. The regulation uses a narrower term. Flight visibility is the average slant distance from the control station at which prominent unlighted objects may be seen and identified by day, and prominent lighted objects may be seen and identified by night. Each word does work. Slant distance means measured along your line of sight, not straight down to the ground. Average means a hazy patch does not set the number on its own. From the control station means where you are standing, not at the airport that happens to publish the weather. And the day and night phrasing means the thing you look for changes after dark: by day you need to identify unlit objects such as a tower or a ridge, by night you need to pick out lights.

14 CFR § 107.51(c) AC 107-2A ¶ 5.12.3

Estimating 3 miles in the field

A statute mile is 5,280 feet, so 3 miles is 15,840 feet, about 2.6 nautical miles. Nobody can eyeball that cold. Use landmarks. Before you launch, find things you know the distance to: a water tower, a ridge line, a radio mast, a highway interchange. Measure the distance from your position on a map or an aeronautical chart. Then look. If you can pick out and identify a landmark at 3 miles, you have your answer. If it is faint or gone, you do not have 3 miles of flight visibility. This is a field technique rather than a regulatory requirement; the regulation sets the standard and leaves the method to you.

Using the envelope below

The drone is yours to drag. The cloud sits on the right with its base high above the ground; the shaded dashed box is the keep-out zone, 500 feet deep under the base and 2,000 feet wide at the side. Four readouts follow you: how far below the base you are, how far beside the cloud’s edge, the visibility, and a verdict. The slider sets flight visibility from 0.5 to 10 statute miles. Verdict logic: you are legal when you are at least 500 feet under the base or at least 2,000 feet from the edge, and the visibility is at least 3.

Three experiments are worth the minute each takes.

1. Park the drone inside the box, then drag straight down. Watch the verdict flip to legal the moment the vertical readout reaches 500. You never changed the horizontal distance.
2. Park it inside the box again, then drag straight left. The verdict flips at 2,000 feet beside, and the vertical readout no longer matters. That is the “or”.
3. Put the drone far outside the box in clear air, so the verdict is legal. Now slide visibility down to 2.5. The verdict goes illegal and nothing about the cloud changed. Clearance and visibility are two separate tests, and failing either one fails the flight.

14 CFR § 107.51(c), (d)

How the test asks about it

Two patterns come up. The first is the numbers straight: a question asks for the minimum distance from clouds, or the minimum flight visibility, with options like 500 below and 2,000 horizontal, 1,000 below and 2,000 horizontal, or 500 below and 1,000 horizontal. Know the pair cold, and know that visibility is 3 statute miles, not nautical miles and not 5.

The second is a scenario in which visibility is the trap. The drone is well clear of the cloud, and the stem hands you a ceiling and a weather report in friendly language. A forecast of broken clouds at 4,000 feet is not the issue; a reported visibility of 2 miles is. Check the cloud clearance, then check the visibility separately, and do not let a clean answer to one hide a failure of the other.

14 CFR § 107.51(c), (d) · AC 107-2A ¶ 5.12.3

Can you get a waiver?

Yes. Section 107.205 lists § 107.51, the operating limitations, among the regulations that a certificate of waiver may deviate from. You would have to show the FAA a proposed operation that can be conducted safely under the terms of the waiver, which in practice means an application with mitigations for the specific hazard, not a bare request for less visibility. The default, and what the exam tests, is the unwaived rule.

14 CFR § 107.205(i) · 14 CFR § 107.200(a)

Where to go next

With the envelope under your fingers, the next question is how you know where the cloud base is on the day. The ceiling comes from the weather report, and reading it is a skill of its own: see decoding METAR and TAF for how a ceiling is reported and what counts as one. Then return to the Regulations study chapter to see how this limit sits beside altitude, speed, and the other operating limits.