• CFR: Code of Federal Regulations, i.e. the US Federal Law.
  • FAR: Federal Aviation Regulations. The FARs are found in CFR under
    • Title 14 (Aeronautics and Space)
    • Title 49 (Transportation)
  • Parts: to the parts of the FAR.
  • AIM: The book is called FAR/AIM. However the AIM is basically a textbook with further information consisting of several topics in individual chapters. AIM is not part of the regulation.

Title => Chapter => Subchapter => Part.

Note that Title 48 of the Code of Federal Regulations (CFR) is titled “Federal Acquisitions Regulations” (also FAR). The two identical acronyms have created confusion, leading the Federal Aviation Administration (FAA) to refer to regulations as "14 CFR part XY" (instead of "FAR part XY"). NoteChapter and Subchapter are not mentioned in

For example:

  • Chapter 1 of Title 14: FAA, Department of Transportation.
  • Subchapter D Airmen, Part 61: "Certification: Pilot, Flight Instructors and Ground Instructors" (14 CFR part 61) for non-certificated flying schools and independent flight instructors.
  • Subchapter H Schools and Other Certificated Agencies, Part 141 "Pilot Schools" (14 CFR part 141) for FAA certified schools.

Flight School: Part 61 vs Part 141

You may get your training under either Part 61 or Part 141. TL;DR: Part 61 does not offer any structured courses or programs, Flight training is done one-on-one with an instructor of your choice. Part 141 is a much more structured curriculum but has lower hour minimums.


  • Part 61 concerns the requirements for certification for pilots, flight instructors and ground instructors. It regulates several types of licenses as to who is eligible, and it establishes the aeronautical knowledge requirements and flight time requirements.
  • Part 141 is oriented more to the regulation of pilot schools. Part 141 schools are required to use a structured training program and a syllabus. Pilot schools may be certified for a variety of courses for pilots and instructors.


  • Part 61 offers more flexibility. Trainees may attend part-time as their personal schedule permits.
  • Part 141 is more like courses you would take in college. It’s rigorous, and requires full-time attention. The training in Part 141 is more formal and more highly regulated. The curriculum must be approved by the FAA.

Hour Requirements:

  • Part 61 requires 40 hours of Private Pilot License flight time and 250 hours of Commercial Pilot License.
  • Part 141 requires 35 hours for private and 190 hours for commercial.

Part 61 vs 91

  • Part 61 deals with training and licensing.
  • Part 91 contains a set of operating and flight rules that civil aircraft pilots must follow. These are the guidelines you must adhere to when flying.

Job Opportunities (Operations): Part 91 vs 121 vs 135

Three parts of the FAR related to aircraft operations: Part 91, 121, 135.

  • Part 91: general aviation.
  • Part 121: scheduled air carriers.
  • Part 135: commuter operations and on-demand operations (also known as charters). Part 135 only applies to aircraft with 30 or fewer seats or a maximum payload capacity of 7,500 pounds, including commercial helicopter operations. Think of private jets, small turbo-propeller aircraft, and commercial helicopters

When you talk about job opportunities:

  • Part 91: some wealthy people buy private jets and you are hired to operate them.
  • Part 91 Subpart K: Fractional Ownership Operations, e.g. PlaneSense.
  • Part 121: you work for the airlines, e.g. mainline (United, Delta, AA), regional (SkyWest, Envoy) and cargo (FedEx or UPS).
  • Part 135: you work for charter companies.


  • part 91 have no legally required rest periods, meaning they can fly their aircraft for days on end without ever taking a break. Under parts 121 and 135, however, this is not the case, and pilots must adhere to strict rest schedules to ensure that they are not fatigued during their operations.
  • Another example is weather minimums. A part 121 or 135 crew cannot legally initiate an approach if the weather is below minimums. Under part 91, however, they are free to do so.
  • One of the most notable distinctions between parts 121 and 135 is the requirement for two pilots on a part 121 operation vs. the allowance for one pilot on a part 135 operation.
  • Passenger identification is not required for domestic flights under part 91. For part 121 or 135 operations, passenger identities need to be verified by the operator, and passengers who are at least 18 years old will be required to provide photo identification.
  • A charter company, for example, may be able to fly their turbo-propeller aircraft under part 91 for a repositioning flight with no passengers, allowing fewer restrictions on that specific flight. Then, when an aspect of part 135 is met (such as a paying passenger onboard), their ops spec for part 135 is enforced.
  • all part 91 restrictions apply to a part 121 operator, but the more restrictive part 121 rules trump their part 91 counterparts.

The FAA’s definition of a scheduled operation is at least “5 round trips per week on at least one route between two or more points according to the published flight schedule.”

Part 23 vs 25

  • Part 23 aircraft: normal, utility, acrobatic, and commuter category airplanes; standards for airplanes weighing 19,000 pounds or less and with 19 or fewer passenger seats.
  • Part 25 defines transport category airplanes.


  • Part 27: utility helicopters.
  • Part 29: transport helicopters.


Aircraft may be operated in several different categories: 91 subpart K Fractional Ownership Operations (91.1001+), 121, 125, or 135