Here are some of the airspaces where FAR 91.215 requires aircraft to have transponders--

(b) ...

(2) All aircraft. In all airspace within 30 nautical miles of an airport listed in appendix D, section 1 of this part from the surface upward to 10,000 feet MSL;

(3) Notwithstanding paragraph (b)(2) of this section, any aircraft which was not originally certificated with an engine-driven electrical system or which has not subsequently been certified with such a system installed, balloon or glider may conduct operations in the airspace within 30 nautical miles of an airport listed in appendix D, section 1 of this part provided such operations are conducted -

(i) Outside any Class A, Class B, or Class C airspace area; and

(ii) Below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport or 10,000 feet MSL, whichever is lower; and

Consider the airspace near Honolulu International Airport (now Daniel K Inouye International Airport), HNL/ PHNL. (Link to sectional chart.)

May an aircraft with no engine-driven electrical system operate at 9500' MSL directly over Wheeler AAF (HHI/PHHI)?

This airspace is within one of the 30-nm Mode C veils described in FAR 91.215 (2).

The intent of the question is to ask whether the "Below the altitude of the ceiling of a Class B or Class C airspace area" clause of 91.215(3)(ii) applies only within the actual lateral boundaries of (i.e. within, above, or below) Class B or C airspace, or throughout the 30-nm circle. Wheeler AAF is within the mode C veil for HNL, but beyond the actual lateral boundaries of any of the Class B airspace. The ceiling of the Class B airspace at HNL is 9000' MSL.

See also related question FAR 91.215 (b)(3)(ii) -- transponders-- does the "or below 10,000' MSL" clause have any practical significance?

  • $\begingroup$ I think the answer has to be "yes". I.e. that the "below the altitude of the ceiling" clause only applies within the lateral limits of whatever Class B or C may be present. Otherwise, which ceiling would apply within the mode C veil near LAX-- the 10,000' ceiling of the LAX Class B, or the 4,800' ceiling of the Burbank Class C? vfrmap.com/… $\endgroup$ Jun 25, 2019 at 15:03
  • $\begingroup$ A similar situation applies at Miami (Class B ceiling 7000' MSL) where we also have Ft Lauderdale Class C airspace w/ a ceiling of 4000' MSL. $\endgroup$ Jun 25, 2019 at 15:09
  • $\begingroup$ Also in the NYC area where we have JFK, Newark, and LaGuardia all with Class B ceilings at 7000' MSL, and Long Island McArthur with a ceiling at 4100' MSL. $\endgroup$ Jun 25, 2019 at 15:22
  • $\begingroup$ Why not contact your local FSDO and seek some clarification? I had no problem talking with them when I was seeking a ferry permit to move an out of annual plane after completing a re-paint. They then went on shutdown for 35 days, but that was not their fault. Turned out to be quicker to just have the paint shop AP/IA do the annual inspection, and sending him copies of logbooks/maintenance done since the prior annual. Only 2 recurring ADs to address, so not too bad. $\endgroup$
    – CrossRoads
    Jun 25, 2019 at 15:34
  • $\begingroup$ The reg could certainly could have been written more clearly to avoid this ambiguity-- for example, as was done in FAR 91.215(b)(4) pertaining to flying ABOVE Class B or C-- "(4) All aircraft in all airspace above the ceiling and within the lateral boundaries of a Class B or Class C airspace area designated for an airport upward to 10,000 feet MSL;" $\endgroup$ Jun 25, 2019 at 15:36

1 Answer 1


Yes, the following statement indicates that aircraft without electrical systems may penetrate the mode C veil at any altitude (presumably excluding cases where the penetration would immediately bring them into Class B or C airspace, or would immediately place them above underlying Class B or C airspace):

"The practical effect of paragraph (b)(3) with respect to your question is that it allows non-equipped aircraft to enter the 30-nautical mile circles surrounding Appendix D, Section 1 airports between the surface and 10,000' MSL and to operate beneath the floors of the associated Class B airspace..."

From this page 2 of this 2006 interpretation from the FAA Office of the Chief Counsel.

  • $\begingroup$ Well, I didn't intend to self-answer, but then I found that interpretation-- makes sense to me. $\endgroup$ Jun 25, 2019 at 16:10

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