⚖ Airspace · FAA Sectional Chart User's GuideAIR-023 · 73 of 261

On an aeronautical chart, airspace altitude limits for controlled airspace are typically depicted as:

AFeet MSL for ceilings and feet AGL for floors, listed separately in chart margin notes.

BAltitude limits use feet AGL for floors and feet MSL for ceilings, stacked as a fraction within the boundary lines.

CA fraction in hundreds of feet MSL, with the ceiling on top and floor on bottom (e.g., 40/SFC means surface to 4,000 MSL).✓

Why →On sectional charts, airspace altitude limits appear as a fraction, ceiling over floor, in hundreds of feet MSL. "40/10" means 1,000 to 4,000 feet MSL, and "SFC" as the floor means the airspace reaches the surface. This notation is used within the boundary lines on the chart for Class B, C, and D airspace.

The trap →Both ceiling and floor values are in feet MSL, not a mix of MSL and AGL. Many students assume floors are in AGL because Part 107 altitude limits are AGL-based, but sectional chart airspace notation is consistently MSL throughout. The only exception is SFC, which means the airspace starts at ground level.

Field note →When reading Class C airspace on a sectional, the inner circle typically shows SFC/4 (surface to 4,000 MSL) and the outer shelf might show 12/4 (1,200 to 4,000 MSL). Understanding this notation tells you exactly which altitudes require authorization.

SOURCE → FAA Sectional Chart User's GuideCHECKED JUL 16ACS II.A.K2MED

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