Part 91 vs Part 135: When You Actually Need a Charter Certificate

One of the most persistent misconceptions in business aviation is that Part 91 and Part 135 are separated by aircraft size, seat count, or turbine versus piston. They are not. A Gulfstream flown for a company's own executives can operate under Part 91, while a single-engine piston carrying a paying passenger may require a Part 135 certificate.

Part 91 contains the general operating and flight rules that apply to nearly all civil aircraft operations in the United States. Part 135 layers a far more demanding certificate, training, maintenance, and oversight regime on top, and it applies when an operation carries persons or property for compensation or hire in commuter or on-demand service.

The question the FAA actually asks is about the nature of the transaction and who controls the flight, not what is parked in the hangar. Getting that answer wrong is the root of most illegal charter enforcement, which we cover in depth in our guide to illegal charter and operational control.

Operators frequently assume that if no invoice is issued, no compensation has changed hands. The FAA has historically read compensation very broadly. It is not limited to money, and it does not require that the operator make a profit.

Reimbursement of costs, exchange of services, goodwill and business advantage, or an accounting entry moving expense between related companies can all be treated as compensation depending on the facts. This is why well-intentioned arrangements between affiliated businesses so often drift into territory that requires a certificate.

Because the analysis is fact-specific and the consequences are severe, this is an area where a written legal opinion from qualified aviation counsel is worth far more than a confident assumption.

The FAA's long-standing framework describes common carriage through four elements: a holding out of a willingness to transport persons or property, from place to place, for compensation or hire. When all four are present, the operation is common carriage and requires the appropriate certificate.

Holding out means signalling to the public that you are available to carry whoever comes along. It does not require advertising. Word of mouth, a broker relationship, a listing on a marketplace, or a pattern of accepting whoever calls can all establish holding out.

Private carriage, by contrast, involves carrying a small number of customers under long-term contracts where the operator has not offered itself to the public generally. The distinction is narrow, heavily fact-dependent, and regularly misjudged.

Operational control means the exercise of authority over initiating, conducting, or terminating a flight. Under Part 135, operational control rests with the certificate holder, and it cannot be delegated to the customer, the aircraft owner, or a management company by contract language alone.

In practice, the FAA looks at who actually decides whether a flight goes: who accepts the trip, who releases it, who can cancel it for weather or maintenance, who employs and directs the crew, and who carries the operational risk. Paperwork that says one thing while day-to-day behaviour says another will not survive scrutiny.

This is also where dry lease arrangements attract attention. A lease that transfers the aircraft but not genuine operational control to the lessee can create an unlicensed charter operation, with liability landing on parties who believed they were structured correctly.

Moving from Part 91 to Part 135 is not a filing exercise. It is the adoption of a supervised operating system. You will need an air carrier certificate and operations specifications defining exactly what you are authorized to do, along with named management personnel such as a Director of Operations, Chief Pilot, and Director of Maintenance.

You will also need an FAA-accepted or approved set of manuals, an approved training program with recurring checks, an approved maintenance program and recordkeeping system, a drug and alcohol testing program, duty and rest limits for crew, and an ongoing surveillance relationship with your local FSDO.

For a realistic view of the timeline and cost, see our breakdown of the Part 135 certification process, and use the Part 135 compliance checklist to see the ongoing obligations that follow certification.

Once you hold a certificate, your manuals become the standard you are measured against. Inspectors compare what your General Operations Manual says against what your crews actually do and what your records show. Drift between the three is one of the most common sources of findings.

That drift is usually not negligence. Regulations change, operations specifications get amended, procedures evolve in practice, and manual revisions lag behind. Without a systematic way to map each manual procedure to the requirement it satisfies, gaps stay invisible until an inspector finds them.

This is the problem Navlyt was built for: mapping your operations manuals to FAA Part 135 requirements, flagging the gaps with cited evidence from your own documents, and tracking each one to closure as a corrective action.