FAR 21.191 — Experimental Airworthiness Certificates
FAR 21.191 lists the purposes for which the FAA issues experimental airworthiness certificates, from R&D and air racing to amateur-built and light-sport aircraft.
In Plain English
FAR 21.191 spells out the specific purposes for which the FAA will issue an experimental airworthiness certificate. An aircraft can't just be flown "experimentally" for any reason — it has to fit one of the listed categories, and the operating limitations attached to the certificate will reflect that purpose.
The approved experimental purposes include:
- Research and development — testing new designs, equipment, installations, techniques, or uses.
- Showing compliance with regulations — flights for type certificates, supplemental type certificates (STCs), major design changes, and function-and-reliability testing.
- Crew training for the applicant.
- Exhibition at air shows and film/TV productions, plus practice and ferry flights.
- Air racing, including practice and travel to events.
- Market surveys, sales demos, and customer crew training (per § 21.195).
- Amateur-built (homebuilt) aircraft — built mostly by the owner for education or recreation.
- Primary category kit-built aircraft assembled without the kit manufacturer's supervision.
- Light-sport aircraft meeting specific kit-built or transition criteria.
Why it matters: as a pilot, the experimental purpose drives the operating limitations in the aircraft's documents — what you can do, where, and with whom on board.
Regulation Text
14 CFR § 21.191§ 21.191 Issue of experimental airworthiness certificates.
Experimental airworthiness certificates are issued for the following experimental purposes:
(a)Testing new aircraft design concepts, new aircraft equipment, new aircraft installations, new aircraft operating techniques, or new uses for aircraft.
(b)Conducting flight tests and other operations to show compliance with the airworthiness regulations including flights to show compliance for issuance of type and supplemental type certificates, flights to substantiate major design changes, and flights to show compliance with the function and reliability requirements of the regulations.
(c)Training of the applicant's flight crews.
(d)Exhibiting the aircraft's flight capabilities, performance, or unusual characteristics at air shows, motion picture, television, and similar productions, and the maintenance of exhibition flight proficiency, including (for persons exhibiting aircraft) flying to and from such air shows and productions.
(e)Participating in air races, including (for such participants) practicing for such air races and flying to and from racing events.
(f)Use of aircraft for purposes of conducting market surveys, sales demonstrations, and customer crew training only as provided in § 21.195.
(g)Operating an aircraft the major portion of which has been fabricated and assembled by persons who undertook the construction project solely for their own education or recreation.
(h)Operating a primary category aircraft that meets the criteria of § 21.24(a)(1) that was assembled by a person from a kit manufactured by the holder of a production certificate for that kit, without the supervision and quality control of the production certificate holder under § 21.184(a).
(i)Operating a light-sport aircraft that—
(1) Has not been issued a U.S. or foreign airworthiness certificate and does not meet the provisions of § 103.1 of this chapter. An experimental airworthiness certificate will not be issued under this paragraph (i) for these aircraft after January 31, 2008;
(2) Has been assembled—
(i) From an aircraft kit; and
(ii) In accordance with manufacturer's assembly instructions that meet an applicable consensus standard; and
(iii) An experimental airworthiness certificate will not be issued under this paragraph (i)(2) for these aircraft after October 22, 2025; or
(3) Has been previously issued a special airworthiness certificate in the light-sport category under § 21.190. An experimental airworthiness certificate will not be issued under this paragraph for these aircraft after October 22, 2025.
(j) [Reserved]
(k)Operating an aircraft of a type that has been certificated under § 21.190 and assembled from an aircraft kit in accordance with manufacturer's assembly instructions that meet an applicable FAA-accepted consensus standard.
(l)Operating an aircraft that previously has been issued a special airworthiness certificate in the light-sport category under § 21.190.
[Amdt. 21-21, 38 FR 6858, May 7, 1968, as amended by Amdt. 21-57, 49 FR 39651, Oct. 9, 1984; Amdt. 21-70, 57 FR 41369, Sept. 9, 1992; Amdt. 21-85, 69 FR 44862, July 27, 2004; Amdt. 21-85, 69 FR 53336, Sept. 1, 2004; Amdt. 21-109, 90 FR 35207, July 24, 2025]
Link to an amendment published at 90 FR 35207, July 24, 2025.
Oral Exam Questions a DPE Might Ask
Q1Name several purposes for which an experimental airworthiness certificate can be issued.
Per FAR 21.191, purposes include research and development, showing compliance with the airworthiness regulations, crew training, exhibition, air racing, market surveys, amateur-built operation, and certain light-sport and kit-built aircraft.
Q2Under what experimental purpose is an amateur-built (homebuilt) aircraft certificated?
Under FAR 21.191(g), for operating an aircraft the major portion of which was fabricated and assembled by persons who undertook the project solely for their own education or recreation.
Q3Can an experimental certificate be issued for sales demonstrations or customer training?
Yes — FAR 21.191(f) allows issuance for market surveys, sales demonstrations, and customer crew training, but only as provided in § 21.195.
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Related Sections in Part 21