Part 107 cloud clearance and weather minimums

The standard Part 107 weather minimums are 3 statute miles of flight visibility, 500 feet below clouds, and 2,000 feet horizontally from clouds. Visibility is assessed from the control station. A convenient memory aid is 3–500–2,000, but the test expects you to apply the numbers to cloud bases, cloud-cover codes, and a planned altitude.

The controlling text is 14 CFR § 107.51. The current Remote Pilot ACS tests basic weather minimums under UA.II.B.K1 and ceiling and visibility under UA.III.B.K1j.

This is independent study material, not FAA guidance or legal advice. Check the current regulation and official weather before an operation.

The exact numbers to know

Under § 107.51(c) and (d), no person may operate a small unmanned aircraft when:

• flight visibility, as observed from the control station, is less than 3 statute miles; or
• the aircraft's distance from clouds is less than 500 feet below the cloud or 2,000 feet horizontally from the cloud.

Notice what the rule does not say:

• It does not substitute nautical miles for statute miles.
• It does not measure visibility from the nearest airport reporting station.
• It does not apply the cloud distance only to a “ceiling.”
• It does not say that a legal condition is automatically safe for your aircraft.

The rule sets a minimum. Wind, gusts, precipitation, temperature, visual line of sight, aircraft documentation, airspace, people, and other operating rules still matter.

Flight visibility is observed from the control station

The METAR may report 10 SM at an airport while fog, smoke, rain, terrain, or local haze reduces visibility at your launch site. Conversely, an airport report some distance away does not mechanically determine what you observe at the control station.

For a test question, use the location and wording given. For an actual flight:

1. obtain current official weather information;
2. observe conditions from the control station;
3. assess the entire planned flight area, not just one direction; and
4. continue monitoring because visibility can change during the operation.

Exactly 3 SM meets the numerical floor because the rule prohibits visibility less than 3 SM. That does not give you operational margin. A conservative limit may be higher depending on terrain, contrast, mission distance, lighting, and likely weather changes.

If you need practice finding the visibility group, use How to read a METAR for Part 107.

Cloud clearance applies to clouds, not just ceilings

Cloud amount and cloud base are different pieces of information.

The FAA uses these common sky-cover codes:

• FEW: more than zero through 2/8 coverage;
• SCT: 3/8 through 4/8;
• BKN: 5/8 through 7/8;
• OVC: 8/8; and
• VV: vertical visibility into a complete obscuration.

For aviation purposes, a ceiling is the lowest broken or overcast layer, or the vertical visibility into an obscuration. FEW and SCT layers are not ceilings. They are still clouds, so the aircraft must maintain the required vertical and horizontal distance from them.

This distinction creates a common distractor. A question may report SCT010 and offer “there is no ceiling” as if that means unrestricted drone flight. No ceiling is not the same as no cloud-clearance requirement.

Convert the cloud code into feet AGL

METAR and TAF cloud-base digits represent hundreds of feet above ground level.

• BKN008 means a broken layer with a base at 800 feet AGL.
• SCT015 means scattered clouds at 1,500 feet AGL.
• OVC030 means overcast at 3,000 feet AGL.
• VV004 means vertical visibility of 400 feet into a complete obscuration.

Keep AGL separate from MSL. A sectional chart may use mean sea level for other values, while METAR cloud bases are reported in hundreds of feet above the reporting station's ground level.

The current FAA AIM weather section is the primary reference for these codes.

Calculate the usable altitude below a cloud

When the question places the aircraft directly under a reported cloud base, subtract the required 500-foot vertical clearance.

Example 1: broken layer at 800 feet AGL

BKN008 gives an 800-foot cloud base. To remain 500 feet below it:

800 - 500 = 300 feet AGL

The cloud rule therefore limits the aircraft to 300 feet AGL directly beneath that layer, even though the general Part 107 altitude limit may otherwise allow 400 feet AGL.

Example 2: overcast at 1,200 feet AGL

OVC012 means a 1,200-foot cloud base:

1,200 - 500 = 700 feet AGL

The cloud clearance alone would permit up to 700 feet below the layer. The normal Part 107 altitude limitation remains 400 feet above ground level unless the operation qualifies for the structure provision or has other authorization. Use the most restrictive applicable limit. In a standard open-area operation, that would normally remain 400 feet AGL.

Example 3: vertical visibility 400 feet

VV004 reports vertical visibility of 400 feet into a complete obscuration. You cannot place an aircraft between the ground and that obscuration while remaining 500 feet below it. Visibility itself may also be below the Part 107 minimum.

Do not force the arithmetic to produce a negative “allowed altitude.” The practical conclusion is that the reported condition does not support an operation beneath that layer under the standard minimum.

Example 4: scattered clouds at 600 feet

SCT006 is not a ceiling, but clouds are reported at 600 feet AGL. Directly beneath one, an aircraft would need to remain at or below 100 feet AGL to preserve 500 feet of vertical separation. It must also remain 2,000 feet horizontally away.

Because a METAR summarizes conditions at a station rather than mapping the position of each cloud, real-world compliance requires observation, planning, and adequate margin—not merely one subtraction.

The 2,000-foot horizontal requirement matters

Students often memorize “500 below” and forget 2,000 horizontal. The aircraft must satisfy both cloud distances.

A low flight is not automatically compliant if a cloud is nearby at roughly the same altitude. In broken or scattered conditions, the remote pilot has to keep the aircraft's planned volume far enough from individual clouds and react if clouds move or develop.

This is another reason a ceiling calculation cannot authorize the flight by itself. The report gives cloud amount and base at a station, but it does not provide a live three-dimensional map of every cloud relative to the aircraft.

Cloud clearance and the 400-foot altitude rule are separate

The same section of Part 107 generally limits the aircraft to 400 feet above ground level, subject to the structure provision. Cloud clearance is an additional constraint.

Use this order:

1. Determine the maximum altitude allowed by § 107.51(b), including whether the structure provision actually applies.
2. Determine the maximum altitude that preserves 500 feet below clouds.
3. Confirm 2,000 feet of horizontal cloud distance.
4. Use the lowest applicable altitude and maintain all other requirements.

The structure provision does not erase cloud clearance. Being within 400 feet of a tall structure may affect the altitude limit, but the aircraft still needs the required distance from clouds.

Ceiling categories do not replace the Part 107 rule

Aviation weather products may describe VFR, MVFR, IFR, or LIFR categories using ceiling and visibility thresholds. Those categories are useful summaries for broad situational awareness, but they are not the text of § 107.51.

For a Part 107 question, apply the actual small-UAS numbers. A reported category does not independently tell you whether the aircraft can maintain 3 SM visibility, 500 feet below clouds, and 2,000 feet horizontally at your control station and mission location.

Combine a METAR and TAF correctly

Suppose the current report is:

METAR KABC 211800Z 16008KT 5SM BR BKN009 17/16 A3001

The METAR reports 5 SM visibility in mist and a broken ceiling at 900 feet AGL. Directly below the layer, cloud clearance limits the aircraft to 400 feet AGL: 900 - 500 = 400.

Now the forecast includes:

TEMPO 2120/2123 2SM BR BKN005

Between 2000Z and 2300Z, temporary conditions may reduce visibility to 2 SM and lower the broken layer to 500 feet. The visibility would be below the Part 107 standard, and there would be no usable space beneath the reported layer that remains 500 feet below it.

A flight planned for 2030Z should not rely on the earlier 5 SM observation while ignoring the forecast temporary group. Learn to put those changes on a timeline in How to read a TAF for Part 107.

Common test traps

Choosing 3 nautical miles

The regulation says 3 statute miles. METAR visibility in the United States is also reported in statute miles.

Adding instead of subtracting

To stay below a cloud, subtract 500 feet from its base. A base at 800 feet produces a maximum of 300 feet directly beneath, not 1,300 feet.

Forgetting the horizontal number

The full memory aid is 3–500–2,000. An answer that mentions only vertical distance is incomplete when the question asks for all weather minimums.

Assuming SCT means unrestricted

Scattered is not a ceiling, but it is a cloud layer. Maintain cloud clearance.

Using the airport report as the legal observation point

The rule measures flight visibility as observed from the control station. METARs inform the decision; they do not relocate the control station.

Treating a minimum as a target

“Legal at exactly the limit” is not the same as a good operational choice. Trends, local variability, aircraft capability, and mission consequences should create margin.

A fast exam method

When a question provides clouds and visibility:

1. Confirm visibility is in statute miles and at least 3.
2. Identify every cloud group and convert its height from hundreds of feet AGL.
3. Find the lowest relevant cloud base.
4. Subtract 500 feet for the vertical limit.
5. Compare that result with the separate altitude limit.
6. Confirm 2,000 feet horizontal distance.
7. Check the mission time against any TAF change group.

Write 3 / 500 / 2,000 on scratch paper before solving. That leaves more attention for the units and timeline.

Review this inside the full Part 107 weather guide, see how it fits the Part 107 test outline, and practice mixed questions in the free demo or Part 107 course.

Official references used

• 14 CFR § 107.51, Operating limitations for small unmanned aircraft
• Remote Pilot — Small UAS Airman Certification Standards, FAA-S-ACS-10B
• Aeronautical Information Manual, Chapter 7
• Aviation Weather Handbook, FAA-H-8083-28B

References checked July 21, 2026. Verify the current rule and current weather before flight.