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Class C upper limit in MSL

Remote Pilot (Part 107) practice question 19 of 21 on Airspace / Classification. ACS element UA.II.A.K1b · difficulty: applied. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONA Class C airspace area surrounds an airport whose field elevation is 600 feet MSL. Using the general dimensions given in the Remote Pilot Study Guide, what is the approximate upper limit of that Class C airspace?

  1. A4,000 feet MSL
  2. B10,600 feet MSL, the same as Class B
  3. C4,600 feet MSL
Show the answer and explanation

Correct answer: C. 4,600 feet MSL

  • A — incorrect 4,000 feet is the height above the airport elevation, not an MSL altitude; the airport elevation must be added.
  • B — incorrect Class B generally tops out at 10,000 feet MSL; Class C uses 4,000 feet above the airport elevation, not 10,000 feet.
  • C — correct Class C generally extends to 4,000 feet above the airport elevation; 600 feet plus 4,000 feet equals 4,600 feet MSL.

BACKGROUND

The Remote Pilot Study Guide describes Class C airspace as generally extending from the surface to 4,000 feet above the airport elevation, charted in mean sea level (MSL). Because the limit is expressed relative to the airport, converting it to MSL requires adding the field elevation. For an airport at 600 feet MSL the top of Class C is therefore about 4,600 feet MSL. The airspace usually consists of a surface area with a five nautical mile radius and an outer circle with a ten nautical mile radius extending from 1,200 feet to 4,000 feet above the airport elevation.

STUDY TIP

When a limit is stated as height above the airport, add the field elevation to get the charted MSL value.

KEY POINTS

  • Class C generally extends to 4,000 feet above the airport elevation.
  • Charted altitudes are in MSL, so add the field elevation.
  • 600 feet plus 4,000 feet gives about 4,600 feet MSL.

SOURCES

  • remote_pilot_study_guide.txt Chapter 2 "Class C Airspace"
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MORE ON AIRSPACE / CLASSIFICATION

SkyDrill is not affiliated with the FAA. This is an original practice item based on 14 CFR part 107, 14 CFR part 89, and the FAA Remote Pilot – Small UAS Study Guide (FAA-G-8082-22). Regulations and handbooks are revised; confirm details against the current edition.