Understanding Commercial Operations: Part 91 vs. Part 135
For single-engine piston aircraft owners and operators looking to delve into commercial aviation, navigating the regulatory landscape can be a complex endeavor. The Federal Aviation Administration (FAA) sets forth distinct rules under Part 91 and Part 135 of the Federal Aviation Regulations (FARs), each with its own set of privileges, limitations, and, most importantly, safety standards.1 Understanding these differences is crucial for anyone considering flying for hire.
PART 91: PERSONAL AND PRIVATE USE
Part 91, or “General Operating and Flight Rules,” primarily governs non-commercial aviation.2 This includes private flights, corporate flight departments (when not “holding out” to the public for hire), and recreational flying. For many aircraft owners, Part 91 offers considerable flexibility.3
Under Part 91, the aircraft owner or pilot in command (PIC) generally assumes responsibility for airworthiness and maintenance. While there are still stringent requirements for annual inspections and adherence to Airworthiness Directives (ADs), the specific maintenance programs are often less prescriptive than those for commercial operations. Pilot qualifications under Part 91 are also less demanding, focusing on recreational or private pilot certificates with appropriate ratings.4
The core limitation of Part 91 is its prohibition on “holding out” to the public for hire. This means you cannot advertise or offer transportation services to the general public for compensation. There are some exceptions, such as certain cost-sharing arrangements or providing flight instruction, but the underlying principle remains: Part 91 is for private operations.5 Violating these rules can lead to severe penalties, including certificate suspension or revocation.6 Many pilots believe that if they are simply being paid to fly someone else’s aircraft, it’s a Part 91 operation. However, if the operator (who may or may not be the pilot) is offering transportation for hire, it falls under commercial regulations. The FAA views such activities with a keen eye, focusing on whether the entity is “holding out” to the public1.
PART 135: THE REALM OF COMMERCIAL CHARTER
Part 135, or “Operating Requirements: Commuter and On Demand Operations and Rules Governing Persons on Board Such Aircraft,” is the regulatory framework for commercial air charter, air taxi, and on-demand services.7 This is where flying for hire truly begins. Obtaining a Part 135 certificate is a significant undertaking, requiring substantial investment in time, resources, and a demonstrable commitment to safety.
While it is technically possible to operate single-engine piston aircraft under Part 135, it comes with considerable challenges, particularly for passenger-carrying operations under Instrument Flight Rules (IFR). The FAA imposes much stricter requirements on Part 135 operators and their aircraft to ensure the highest level of safety for paying passengers.8 These requirements encompass:
MAINTENANCE AND AIRWORTHINESS
Part 135 mandates a rigorous maintenance program, often far more extensive than what is required under Part 91.9 This includes more frequent inspections, detailed record-keeping, and the implementation of FAA-approved maintenance schedules.10 Aircraft must often meet specific equipment requirements, such as redundant systems, to be approved for Part 135 operations, especially for IFR flights.11 For piston singles, this might include dual electrical systems, dual vacuum pumps, or an approved three-axis autopilot, which are not typically standard on many Part 91 aircraft.
PILOT QUALIFICATIONS AND TRAINING
Pilots operating under Part 135 must meet significantly higher experience and training requirements.12 This typically includes holding an Airline Transport Pilot (ATP) certificate or a commercial pilot certificate with extensive flight hours, including specific cross-country and night flight time. Furthermore, Part 135 pilots undergo regular proficiency checks, written or oral tests, and recurrent training to maintain their qualifications and ensure they are well-versed in aircraft systems, emergency procedures, and regulatory compliance.13 This rigorous training builds a strong foundation of consistency in operational practices, a key principle of safety.
OPERATIONAL CONTROL AND DOCUMENTATION
Part 135 operators are required to establish an FAA-approved Operations Specifications (OpSpecs) manual, which details every aspect of their operation, from maintenance procedures and pilot training to dispatch and flight following.14 This extensive documentation ensures that all aspects of the commercial operation are standardized and transparent to the FAA. This level of oversight provides social proof of an operator’s commitment to safety, building trust with clients. The FAA conducts continuous oversight, verifying that the operator consistently adheres to these established procedures.
INSURANCE AND LIABILITY
Commercial operations under Part 135 carry a significantly higher level of liability. As such, operators are required to carry substantial liability insurance to protect passengers and third parties in the event of an incident. This is a non-negotiable aspect of Part 135 certification.
THE AERO CENTER ADVANTAGE: REDUCING DOWNTIME
Whether you operate under Part 91 or are pursuing Part 135 certification, reliable and efficient aircraft maintenance is paramount. This is where The Aero Center distinguishes itself. We understand that aircraft downtime directly impacts your operational capabilities and profitability.15 That’s why we pride ourselves on being the only 24/7 maintenance center in California, Arizona, and Nevada.
Our unwavering commitment to keeping your aircraft flying is a testament to our authority in the aviation maintenance field. With a team of highly skilled and experienced technicians, we are equipped to handle everything from routine inspections to complex repairs on single-engine and twin-piston aircraft. We know that every hour your aircraft is on the ground is an hour it’s not generating revenue or serving your mission. Our 24/7 availability ensures that we can address your maintenance needs around the clock, minimizing disruptions and maximizing your aircraft’s operational availability. This commitment to swift, high-quality service fosters consistency in your aircraft’s readiness, allowing you to maintain a predictable operational schedule.
Our dedication to prompt service and expert care has earned us the trust of countless aircraft owners and operators throughout California, Arizona, and Nevada. Our clients consistently attest to our professionalism and efficiency, providing strong social proof of our reliable service. When you choose The Aero Center, you’re choosing a partner that understands the critical importance of keeping your aircraft airworthy and ready for flight, day or night.
CONCLUSION
While Part 91 allows for personal and private use of single-engine piston aircraft, the world of “flying for hire” falls squarely under the more rigorous Part 135 regulations. Obtaining and maintaining a Part 135 certificate is a demanding but necessary step for those looking to engage in commercial air services. The heightened requirements for maintenance, pilot qualifications, and operational oversight are all designed to ensure the utmost safety for paying passengers.
Regardless of your operational part, consistent and reliable maintenance is the backbone of any successful aviation endeavor. The Aero Center, with its 24/7 availability and deep expertise in single-engine and twin-piston aircraft, is your trusted partner in maintaining airworthiness and minimizing downtime across California, Arizona, and Nevada.
Footnotes
- FAA. “Advisory Circular 120-12A – Private Carriage Versus Common Carriage.” Federal Aviation Administration, https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentid/22026
- eCFR. “14 CFR Part 135 — Operating Requirements: Commuter and on Demand Operations and Rules Governing Persons on Board Such Aircraft.” Electronic Code of Federal Regulations, https://www.ecfr.gov/current/title-14/chapter-I/subchapter-G/part-135
- Stratos Jet Charters. “What You Need to Know About Part 135.” Stratos Jets Blog, https://www.stratosjets.com/blog/what-you-need-to-know-about-part-135/
- Pilot Institute. “Differences Between FAA Part 91, 121, and 135 in Aviation.” Pilot Institute Blog, https://pilotinstitute.com/part-91-vs-121-vs-135/
The Aero Center is located at William J. Fox Airfield KWJF | Lancaster, CA. Contact us at 209.885.6950 for questions or appointments.