FAA-H-8083-25C, ch. 12 and FAA-G-8082-22

Stable air vs unstable air

Atmospheric stability decides whether you get smooth, hazy flying or bumpy, clear flying. Learn the two columns for the test.

Part 107, explained › Weather · Last reviewed October 25, 2026 against the eCFR and faa.gov. UAV Campus is not affiliated with the FAA.

What is the difference between stable and unstable air?

Stable air resists vertical motion and gives stratiform clouds and fog, continuous precipitation, smooth air and fair to poor visibility. Unstable air lets parcels keep rising and gives cumuliform clouds, showery precipitation, rough air (turbulence) and good visibility, except in blowing obstructions.

Atmospheric stability is the property of the air that either enhances or suppresses vertical motion of air parcels, and it determines which type of clouds and precipitation a pilot will meet. Stability of an air mass determines its typical weather characteristics.

An air mass passing over a warmer surface is warmed from below, convective currents form, and the result is an unstable air mass with good surface visibility. An air mass passing over a colder surface creates a stable air mass with poor surface visibility, because smoke, dust and other particles cannot rise out of it. A stable air mass can produce low stratus clouds and fog.

Sources: FAA-H-8083-28B, p. 154 · FAA-H-8083-25C (PHAK), p. 302 · Remote Pilot Study Guide, p. 34

What the FAA says

FAA-H-8083-28B, p. 154

Atmospheric stability is the property of the ambient air that either enhances or suppresses vertical motion of air parcels and determines which type of clouds and precipitation a pilot will encounter.

Remote Pilot Study Guide, p. 34

Stability of an air mass determines its typical weather characteristics.

FAA-H-8083-25C (PHAK), p. 302

An air mass passing over a warmer surface is warmed from below, and convective currents form, causing the air to rise. This creates an unstable air mass with good surface visibility. Moist, unstable air causes cumulus clouds, showers, and turbulence to form.

FAA-H-8083-25C (PHAK), p. 302

Conversely, an air mass passing over a colder surface does not form convective currents but instead creates a stable air mass with poor surface visibility.

Sources: FAA-H-8083-28B, p. 154 · Remote Pilot Study Guide, p. 34 · FAA-H-8083-25C (PHAK), p. 302 · FAA-H-8083-25C (PHAK), p. 302

Exam traps

  • Unstable air has good surface visibility and turbulence, while stable air has poor visibility and smooth air.
  • Stable air goes with stratiform clouds, fog and continuous precipitation; unstable air goes with cumuliform clouds and showers.
  • An air mass moving over a warmer surface becomes unstable, and one moving over a colder surface becomes stable.
  • Visibility is poor in stable air because smoke, dust and other particles cannot rise out of the air mass and stay trapped near the surface.

Quick quiz: 3 questions

Similar to the FAA test, not the actual test questions. Each answer shows its FAA source.

Question 1 of 3

What are characteristics of unstable air?

  1. A Turbulence and good surface visibility.
  2. B Turbulence and poor surface visibility.
  3. C Nimbostratus clouds and good surface visibility.
Show the answer
Answer: A. Turbulence and good surface visibility.

Unstable air is characterized by cumuliform clouds and fog, showery precipitation, rough air, and good visibility. Use the attached cheat sheet for reference.

FAA sources: FAA-H-8083-25C ch. 12, Atmospheric Stability · FAA-H-8083-25C ch. 12, Air Masses

Question 2 of 3

What is a characteristic of stable air?

  1. A Unlimited visibility.
  2. B Stratiform clouds.
  3. C Cumulus clouds.
Show the answer
Answer: B. Stratiform clouds.

Stable air is characterized by stratiform clouds and fog, continuous precipitation, smooth air, and fair to poor visibility. Use the attached cheat sheet for reference.

FAA source: FAA-H-8083-25C ch. 12, Air Masses

Question 3 of 3

What are the characteristics of stable air?

  1. A Good visibility and steady precipitation.
  2. B Poor visibility and intermittent precipitation.
  3. C Poor visibility and steady precipitation.
Show the answer
Answer: C. Poor visibility and steady precipitation.

Stable air is characterized by stratiform clouds and fog, continuous precipitation, smooth air, and fair to poor visibility. Use the attached cheat sheet for reference.

FAA source: FAA-H-8083-25C ch. 12, Air Masses

Which clouds mean unstable air?

Cumuliform clouds go with unstable air. Towering cumulus clouds indicate areas of instability, and the air around and inside them is turbulent.

Sources: Remote Pilot Study Guide, p. 34 · FAA-H-8083-25C (PHAK), p. 300

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More on this topic: Part 107 weather, task by task.