What is the purpose of the "121 rules" in aviation?

The "121 rules" refer to the regulations established by the Federal Aviation Administration (FAA) that govern domestic air carriers and commercial operators. These rules are part of Title 14 of the Code of Federal Regulations and specifically focus on the operational standards that commercial airlines must adhere to, including aspects such as aircraft maintenance, flight operations, and safety protocols. The purpose is to ensure a high level of safety and professionalism in commercial aviation, thus protecting passengers, crew, and the integrity of the aviation system as a whole.

The options concerning general aviation, international flight procedures, and private pilot certificates pertain to different sets of regulations or standards within the aviation industry that do not specifically address the operational standards for commercial air carriers. Thus, they do not align with the primary intent and scope of the "121 rules." This distinction solidifies the understanding that the "121 rules" are uniquely focused on commercial aviation operations.