Section 21.175 - Airworthiness certificates: classification(a) Standard airworthiness certificates are airworthiness certificates issued for aircraft type certificated in the normal, utility, acrobatic, commuter, or transport category, and for manned free balloons, and for aircraft designated by the FAA as special classes of aircraft.(b) Special airworthiness certificates are primary, restricted, limited, light-sport, and provisional airworthiness certificates, special flight permits, and experimental certificates.Amdt. 21-21, 33 FR 6858, May 7, 1968, as amended by Amdt. 21-60, 52 FR 8043, Mar. 13, 1987; Amdt. 21-70, 57 FR 41368, Sept. 9, 1992; Amdt. 21-85, 69 FR 44861, July 27, 2004