Reading Class E Floors & Shading
~12 min read · Use magenta/blue vignettes and shading to find the airspace floor above any point.
Sectional charts encode airspace floors in shading and line styles, and the exam asks you to stand at a point on the chart and name the airspace above it. Master four marks: solid lines, dashed lines, magenta vignette, and blue vignette.
The line vocabulary
Solid blue lines outline Class B shelves; solid magenta outlines Class C. Each shelf carries numbers like 100/40 — ceiling 10,000 MSL over floor 4,000 MSL (SFC as the bottom number means the shelf starts at the surface). Dashed blue encloses Class D (the number in brackets is its ceiling in hundreds of feet MSL). Dashed magenta encloses Class E that begins at the surface — the E2 surface areas that require sUAS authorization.
- Solid blue = B, solid magenta = C — read the fraction: ceiling/floor in hundreds of feet MSL
- Dashed blue = D, ceiling in brackets, e.g. [25] = 2,500 MSL
- Dashed magenta = Class E to the surface (authorization required)
The vignettes: where E's floor drops
The soft gradient bands are vignettes. Magenta vignette (fuzzy magenta fading inward): inside the band, Class E begins at 700 ft AGL — the transition area around instrument approaches. Blue vignette: on the hard side Class E begins at 1,200 ft AGL, and outside it, controlled airspace begins even higher (common out west). Where no vignette or surface area applies, E generally starts at 1,200 ft AGL by default in most of the contiguous US.
- Inside magenta vignette: G up to 700 AGL, E above
- Default elsewhere: G up to 1,200 AGL, E above
- A sub-400-ft sUAS flight under a 700/1,200 floor is in Class G
Why a drone pilot cares
Your 400-ft world usually sits entirely in Class G — the floors matter because they tell you when it does NOT: dashed magenta or dashed blue at your location means controlled airspace at the surface and an authorization requirement. Reading floors also disciplines your AGL math: shelf altitudes print in MSL, terrain elevation converts them to heights above your launch point.
Worked example
Your launch point sits inside a magenta vignette band, 6 NM outside a dashed-magenta ring that surrounds an instrument airport. You will orbit a cell tower at 380 ft AGL. What airspace are you in, and is authorization required?
Inside the magenta vignette, Class E starts at 700 ft AGL; below that is Class G. You are outside the dashed-magenta ring, so the E-to-the-surface area does not cover you. At 380 ft AGL you operate wholly in Class G — no authorization needed. Had the job been 2 NM further toward the airport, inside the dashed magenta, the same 380-ft flight would sit in surface Class E and require a LAANC/DroneZone authorization before launch.
Common exam pitfalls
Reading shelf numbers as AGL.
Chart altitudes like 100/40 are MSL in hundreds of feet. Convert with local terrain elevation to know heights above ground.
Treating the magenta vignette as a restriction zone.
The vignette only lowers the Class E floor to 700 AGL — flight below that floor remains Class G and authorization-free.
Confusing dashed magenta with the vignette.
Dashed magenta = E at the SURFACE (authorization required). Fuzzy magenta vignette = E at 700 AGL (no authorization below).
Sharp lines touch the ground; fuzzy bands float at 700.
Recap
- Solid blue/magenta: B/C shelves, numbers = ceiling/floor in hundreds of feet MSL
- Dashed blue: Class D with ceiling in brackets
- Dashed magenta: Class E from the surface — sUAS authorization required
- Magenta vignette: E floor drops to 700 AGL (G below)
- Default E floor elsewhere: 1,200 AGL
- Sub-400-ft flights are in G unless a surface area (dashed line) covers the spot
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