◉ OBSERVED — FAA airspace classification reference. Geometry from FAA ArcGIS Open Data.
Controlled & Uncontrolled Airspace
A
Class A — 18,000 ft MSL – FL600
IFR only
Controlled — entire CONUS above FL180
B
Class B — SFC – 10,000 ft MSL
ATC clearance required
Upside-down wedding cake around primary hub airports
C
Class C — SFC – 4,000 ft AGL
Radio contact required
Around airports with approach control
D
Class D — SFC – 2,500 ft AGL
Radio contact required
Around airports with operating control tower
E
Class E — Varies (1,200 ft – FL180)
IFR: controlled
Transition, en-route, and surface areas
G
Class G — SFC – 1,200 ft AGL
Uncontrolled
Below Class E floors where Class E not designated
Special Use Airspace (SUA)
Restricted (R-)
Entry prohibited/restricted without permission
Warning (W-)
Hazardous activities — VFR flight cautioned
MOA
Military Operations Area — IFR separation not guaranteed
Alert (A-)
High density military training — not prohibited
Prohibited (P-)
Flight prohibited for security/national interest
National Security Area
Voluntary avoidance requested