What is the lateral dimension of Class C airspace, and why does a remote pilot need to understand its layers?

Why →Class C airspace typically consists of two concentric circles: an inner circle of 5 NM radius from surface to 4,000 feet AGL, and an outer circle of 10 NM radius from 1,200 feet AGL to 4,000 feet AGL. Understanding the layered structure matters for drone pilots because operations below the outer shelf floor (below 1,200 AGL, beyond 5 NM) may NOT require authorization, while operations inside the inner circle or above the outer shelf floor require prior authorization.

The trap →Class C is not a single uniform circle. It is a layered "upside-down wedding cake" shape. The outer shelf does not reach the surface. Operations beyond 5 NM but below 1,200 feet AGL may be outside the controlled airspace entirely, depending on exact altitude and position.

Field note →In planning apps like Aloft, always verify your exact location and altitude against the airspace overlay. Hovering at 200 feet AGL at 7 NM from a Class C airport might be in or out of the outer shelf depending on the exact floor altitude at that location. Check the sectional chart notation.