2.3 Class C and Class D Airspace
Key Takeaways
- Class C: solid magenta lines, 5 NM inner core + 10 NM outer shelf, typically up to 4,000 ft AGL.
- Class D: dashed blue lines, ~4 NM radius, typically up to 2,500 ft AGL, only active when tower is operating.
- Both Class C and Class D require prior ATC authorization for Part 107 operations.
- When a Class D tower closes, airspace may revert to Class E surface area or Class G.
- LAANC is available at most Class C and D airports for near-real-time authorization.
2.3 Class C and Class D Airspace
Class C and Class D airspace surround airports that are busy but not at the level of Class B airports. Understanding their differences is important for both the exam and operational planning.
Class C Airspace
Class C airspace surrounds airports with operational control towers, radar approach control, and a minimum level of IFR operations or passenger enplanements.
Dimensions:
- Inner core (surface area): Surface to typically 4,000 feet AGL, extending 5 nautical miles from the airport
- Outer shelf: From typically 1,200 feet AGL to 4,000 feet AGL, extending 10 nautical miles from the airport
- Outer area (not charted): 20 NM from airport — radar service available but not depicted
Identification on Sectional Charts:
- Depicted with solid magenta lines
- Altitude labels show ceiling/floor in hundreds of feet MSL
- SFC under the inner core indicates the floor extends to the surface
Part 107 Requirements:
- Prior ATC authorization required (through LAANC or DroneZone)
- Must comply with all conditions of the authorization
Class D Airspace
Class D airspace surrounds airports with an operational control tower that do not meet the criteria for Class B or C.
Dimensions:
- Typically from the surface to 2,500 feet AGL
- Extends approximately 4 nautical miles from the airport (tailored to local needs)
- Shape is typically cylindrical (simpler than Class B or C)
Identification on Sectional Charts:
- Depicted with dashed blue lines
- Altitude shown in a blue box: e.g., [25] means ceiling of 2,500 feet MSL
- The number in the box represents the ceiling in hundreds of feet MSL
Part 107 Requirements:
- Prior ATC authorization required (through LAANC or DroneZone)
- Must comply with all conditions of the authorization
Comparison: Class C vs. Class D
| Feature | Class C | Class D |
|---|---|---|
| Chart depiction | Solid magenta lines | Dashed blue lines |
| Typical shape | Two-layer (inner + outer shelf) | Single cylinder |
| Surface radius | 5 NM | ~4 NM |
| Ceiling | Usually 4,000 ft AGL | Usually 2,500 ft AGL |
| Radar service | Required | Not required |
| Part 107 auth required | Yes | Yes |
| LAANC available | At most locations | At most locations |
Satellite Airports Within Class B, C, or D
Some smaller airports exist within the boundaries of larger airports' controlled airspace. When operating near these:
- Check both the primary airport and satellite airport airspace designations
- You may need authorization from the larger airport's ATC even if operating near the satellite
- UAS Facility Maps will show approved altitudes considering both airports
When Class D Becomes Class E or G
Class D airspace is only active when the control tower is operating. When the tower closes:
- Class D may revert to Class E surface area (if designated) or Class G
- Check the Airport/Facility Directory (Chart Supplement) for tower operating hours
- If the airspace reverts to Class E surface area, you still need authorization
- If it reverts to Class G, no authorization is needed
For the Exam: Remember — solid magenta = Class C, dashed blue = Class D. Both require authorization. Class D may revert when the tower closes.
Class C airspace is depicted on sectional charts with:
Class D airspace typically extends from the surface to approximately:
When a Class D airport control tower closes, the airspace may: