In aviation weather, how is "ceiling" defined?
AThe maximum altitude at which an aircraft can operate under VFR conditions.
BThe height above ground of the lowest cloud layer reported as broken (BKN) or overcast (OVC).✓
CThe height of the highest cloud layer visible from the surface.
Why →Ceiling is the height AGL of the lowest layer covering more than half the sky. Specifically BKN (5–7/8) or OVC (8/8). FEW and SCT layers do NOT constitute a ceiling. The ceiling directly determines IFR vs. VFR conditions and limits the usable airspace below the 500-foot cloud clearance requirement.
The trap →FEW and SCT layers never make a ceiling; they cover half the sky or less. And it is the lowest qualifying layer that matters, not the highest visible one.
Field note →With a 1,500-foot ceiling and the 500-foot below-cloud rule, effective maximum altitude is 1,000 feet AGL. Still above the Part 107 400-foot limit. But when ceilings drop below 900 feet, your 400-foot altitude cap becomes the binding constraint on cloud clearance.
SOURCE → FAA Meteorology / PHAK Chapter 12CHECKED JUL 16ACS III.A.K1MED