If a certificate holder operating under this part permits any aircraft owned or leased by that holder to be engaged in any operation that the certificate holder knows to be in violation of Sec. 91.19(a) of this chapter, that operation is a basis for suspending or revoking the certificate. [Doc. No. 28154, 60 FR 65926, Dec. 20, 1995] Subpart B--Certification Rules for Domestic and Flag Air Carriers [Reserved] Subpart C--Certification Rules for Supplemental Air Carriers and Commercial Operators [Reserved] Subpart D--Rules Governing All Certificate Holders Under This Part [Reserved]