AhaBulbStuff Everyone Should Know
AhaBulb: Stuff Everyone Should Know · ahabulb.com/pilot-mode-c-veil-30nm

The Mode C veil requires an altitude reporting transponder within how far of listed major airports?

30 nautical miles, from the surface to 10,000 feet MSL.

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  1. 10 nautical miles
  2. 30 nautical miles ✔
  3. 20 nautical miles

Why: Rule 91.215 requires an altitude reporting transponder within 30 nautical miles of airports listed in Appendix D, section 1, mostly Class B airports. Since 2020, ADS-B Out is required in that same airspace.

Huh, didn't know that: Sectional charts mark the 30 NM Mode C area with a solid magenta line around the Class B airport.

The dad joke
Why did the airplane wear a veil? It was going to a Mode C wedding.
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References

Answer: 30 nautical miles. Rule 91.215 requires an altitude reporting transponder within 30 nautical miles of airports listed in Appendix D, section 1, mostly Class B airports. Since 2020, ADS-B Out is required in that same airspace.

  1. 14 CFR 91.215 ATC transponder and altitude reporting equipment (eCFR) www.ecfr.gov/current/title-14/chapter-I/subchapter-F/part-91/subpart-C/section-91.215
    In all airspace within 30 nautical miles of an airport listed in appendix D, section 1 of this part
    Checked 2026-10-09.

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FlyingUnless ATC says otherwise, which transponder code does a VFR pilot use?FlyingWhich transponder code tells ATC your two-way radio has failed?FlyingBefore using a required ATC transponder, how recently must it have been tested and inspected?

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