Ceiling

Ceiling in aviation is the height AGL of the lowest layer of clouds reported as broken (BKN, 5-7 oktas) or overcast (OVC, 8 oktas). Clouds reported as few (FEW) or scattered (SCT) do not constitute a ceiling.

Ceiling is critical for approach and landing: many instrument approach procedures have minimum ceiling requirements. In METARs, ceiling is determined by the lowest broken or overcast layer. A "sky clear" or "no ceiling" report means no cloud layer meets the ceiling definition.