All Parts Part 135 Subpart B—Flight Operations § 135.107
§ 135.107

Flight attendant crewmember requirement

No certificate holder may operate an aircraft that has a passenger seating configuration, excluding any pilot seat, of more than 19 unless there is a flight attendant crewmember on board the aircraft.

Sourced from eCFR · Title 14 CFR · for educational reference only — fly the latest regs.