Ceiling is the height above ground level (AGL) of the lowest layer of clouds that covers more than half the sky. Pilots and controllers use it to quickly assess how much usable vertical space exists between the ground and the overcast above.
How It Works#
Cloud cover is reported in eighths, called oktas. A ceiling exists when a layer covers 5 or more oktas (more than half the sky). Layers reported as "few" (1–2 oktas) or "scattered" (3–4 oktas) do not count as a ceiling.
The ceiling is always measured in feet AGL, not above mean sea level (MSL). This matters because pilots need to know how much room they have above the terrain, not above an arbitrary reference point at sea level.
Ceilings appear in weather reports and forecasts using specific codes. In a METAR (a standardized hourly weather observation), a ceiling is labeled "BKN" (broken, 5–7 oktas) or "OVC" (overcast, 8 oktas). A METAR reading of BKN015 means a broken ceiling at 1,500 feet AGL.
Ceiling can also shift quickly. A reported ceiling of 2,500 feet can drop to 800 feet within minutes as weather moves through. Pilots treat ceiling as a dynamic value, not a fixed one.
Example in Aviation#
A student pilot planning a local training flight checks the METAR for her home airport. It reads OVC008, meaning an overcast ceiling at 800 feet AGL. Basic VFR (Visual Flight Rules) flight in controlled airspace requires a minimum ceiling of 1,000 feet. Her flight is not legal under VFR, so she cancels or waits for conditions to improve.
A commercial airline crew facing the same airport on approach will check the published instrument approach minimums instead. If their approach requires a ceiling of at least 200 feet and the reported ceiling is 300 feet, they can legally attempt the approach.
Why It Matters#
Ceiling is one of the two primary weather values that determine whether flight is possible under VFR or requires IFR (Instrument Flight Rules). The other is visibility. Together, they define whether conditions are VMC (Visual Meteorological Conditions) or IMC (Instrument Meteorological Conditions).
Getting the ceiling wrong has real consequences. A VFR pilot who continues into a lowering ceiling risks becoming trapped in clouds without the training or equipment to navigate safely. Understanding ceiling limits, and respecting them, is a core part of weather decision-making for every pilot.
Key Takeaways#
- Ceiling is the height AGL of the lowest cloud layer covering more than half the sky.
- Only BKN (broken) and OVC (overcast) layers count as a ceiling.
- Ceiling is reported in feet AGL in METARs and forecasts.
- VFR flight in controlled airspace generally requires a ceiling of at least 1,000 feet.
- Ceiling can change rapidly, so pilots check current reports close to departure.