Part 91 vs. Part 135: Choosing the Right Operating Model
Choosing between Part 91 and Part 135 is one of the most consequential decisions an aircraft owner or operator can make. The operating model determines how the aircraft may be used, how costs are managed, how risk is allocated, and how the FAA evaluates the operation. While both models support legitimate business aviation operations, they serve different purposes and carry different regulatory obligations.
Understanding the distinction between Part 91 vs Part 135 begins with the role of compensation and operational control. Part 91 governs non-commercial operations conducted in support of an owner’s internal business or personal needs. Part 135 governs commercial on-demand operations where transportation is provided to others for compensation or hire. The difference is not philosophical. It is regulatory, enforceable, and closely scrutinized by the FAA.
Part 91 offers flexibility that appeals to many aircraft owners. Operators maintain broad discretion over scheduling, routing, and operational decisions. Compliance requirements exist, but they are less prescriptive than those under Part 135. For companies using aircraft solely to support internal travel, this model often aligns well with business needs and organizational structure.
However, Part 91 flexibility has clear boundaries. Cost sharing, aircraft availability to third parties, and leasing arrangements are tightly regulated. When flights begin to resemble charter activity, even unintentionally, the operation may fall outside the scope of Part 91. This is where many compliance issues arise within business aviation operations.
Part 135 allows operators to offer transportation to others for compensation, including charter and on-demand services. This operating model opens revenue opportunities and enables broader aircraft utilization. In exchange, the FAA imposes significantly higher oversight. Operators must obtain certification, maintain approved manuals, implement structured training programs, and demonstrate continuous compliance across maintenance, crew management, dispatch, and operational control.
Charter compliance under Part 135 is built around accountability and consistency. The certificate holder must retain operational control over flights, crews, and risk management decisions. These requirements are designed to protect passengers and ensure standardized operations, particularly as utilization increases and customers change frequently.
For aircraft owners considering Part 135, the advantages are clear. Charter revenue can offset ownership costs, increase aircraft utilization, and support business objectives. However, these benefits come with added complexity. Management structure, staffing, documentation, and compliance oversight all expand under Part 135. Owners must be prepared for the operational and cultural shift that accompanies certification.
One of the greatest risks occurs when operators attempt to blend elements of both models without fully committing to either. Improper dry leasing, affiliated entity use, or cost recovery arrangements that retain owner control can trigger FAA enforcement action. The FAA evaluates how an operation functions in practice, not how it is described in agreements. When Part 91 operations cross into charter-like activity, the consequences can be significant.
This makes informed decision-making essential. Owners should evaluate how the aircraft is used today, how they intend to use it in the future, and how much regulatory responsibility they are prepared to accept. For some, remaining fully compliant under Part 91 provides clarity and reduced exposure. For others, pursuing Part 135 certification aligns better with long-term objectives.
Private aviation consulting often plays a role in this evaluation. An experienced, objective review can help owners understand compliance exposure, assess operational readiness, and determine whether Part 135 is appropriate. This is particularly valuable for operators approaching the limits of Part 91 or considering charter partnerships.
The decision between Part 91 and Part 135 is not solely about revenue or flexibility. It is about governance, risk tolerance, and operational discipline. Both models can support safe and efficient operations when implemented correctly. Problems arise when assumptions replace analysis or when regulatory boundaries are misunderstood.
Business aviation operations benefit from clarity. When owners understand the regulatory framework governing their aircraft, they can make decisions that support safety, compliance, and long-term sustainability. Whether operating privately under Part 91 or commercially under Part 135, alignment between intent and structure protects both the operation and those responsible for it.
Choosing the right operating model requires honest assessment and careful planning. With clear understanding of the advantages and risks of each, aircraft owners can select a path that supports their mission while maintaining regulatory confidence and operational integrity.
