Part 1 Definitions and Abbreviations ; Part 63 Certification : Flight Crewmembers Other than Pilots ( Flight Engineer ) ; Part 65 Ceritification : Airmen Other than Flight Crewmembers ( Dispatcher ) ; Part 91 General Operating and Flight Rules : Subpart K ; Part 119 Certification : Air Carriers and Commercial Operators ; Part 120 Drug and Alcohol Testing Program ; Part 121 Operating Requirements : Domestic , Flag & Supplemental Operations ; Part 135 Operating Requirements : Commuter and on Demand Operations ; Part 175 Hazardous Materials : Carriage by Aircraft ; Part 1544 Aircraft Operator Security : Air Carriers and Commercial Operators