Part 135 vs Part 91: Who Legally Flies You

Every few weeks someone forwards us a quote that sits well under the market and asks whether it is real. Usually it is real in the narrow sense that an aircraft exists and a person will fly it. The question underneath it is Part 135 vs Part 91, and it is the one safety question that gets settled before anyone looks at an audit badge, because one of those rule sets permits selling a flight to the public and the other one flatly does not.

Here is the plain version from the desk: what each rule set covers, why the line blurs in the fourth quarter, and the questions that settle it in about ninety seconds.

The distinction in one line

Part 91 is the FAA's general operating rules. It covers private flying. An owner flying their own aircraft, a corporate flight department moving its own employees, a friend riding along. Nobody is paying for carriage, and the rules are written accordingly. There is no FAA-issued operating certificate behind a Part 91 flight, no charter style duty and rest ceiling, no approved maintenance program in the Part 135 sense.

Part 135 is commercial charter. The operator holds a certificate issued by the FAA, carries operations specifications that name every aircraft and every type of flying it is approved to do, and answers to an assigned principal operations inspector. If money is changing hands for carrying you somewhere, Part 135 (or Part 121, the airline rule set) is the lawful path. There is no clever third option in which an owner sells seats on a Part 91 airplane because the schedule happened to line up nicely.

JetNine sits next to that structure rather than inside it. We hold Part 295 authority as an indirect air carrier, which means we arrange the flight and a Part 135 certificate holder operates it. Our name is on the quote, their certificate is on the flight, and the written floor every one of those certificate holders clears before a booking is eligible lives on our safety standards page.

What the certificate actually buys you

The certificate is not paperwork for its own sake. Operating under Part 135 means, at minimum:

• Crew duty and rest limits with teeth. Flight time, duty time and required rest are capped and tracked, so no one is legally able to grind through a nineteen hour day and then fly a night approach.
• A maintenance program the FAA approved, with inspection intervals tied to that program rather than to whatever the owner considers reasonable this month.
• Recurrent crew training and checking, on type, in an approved program.
• Drug and alcohol testing for safety sensitive personnel.
• Operational control held by the certificate holder, meaning one named entity is legally responsible for the decision to launch, delay or cancel.

Part 91 requires none of that in the same form. This is not an insult to Part 91. It is the correct rule set for what it covers, and some of the most disciplined flight departments in the country operate under it with standards that exceed the charter minimum. The problem is never Part 91 itself. The problem is a Part 91 aircraft being sold as though it were a charter, because then you have paid charter money for an operation with none of the charter structure behind it, and no certificate holder standing between you and a bad decision.

Operational control is the tell

When the FAA looks at a suspect flight, it does not start with the invoice. It starts with a question: who had operational control? Who decided the flight would go, chose the crew, dispatched the aircraft, and bore the responsibility if it went wrong?

On a legitimate charter, the answer is the Part 135 certificate holder, every time. On an illegal charter, the answer gets slippery. The aircraft owner arranged it. A management company handled the crew. A broker put the parties together and took a margin. Nobody in the chain holds a certificate covering that flight, and everybody assumes somebody else was responsible.

Dry lease arrangements are where this most often goes sideways. A genuine dry lease hands the aircraft to the lessee, who then provides their own crew and holds operational control. A dry lease in which the owner or manager conveniently supplies the crew and runs the trip is not a dry lease. It is a charter wearing a paper costume, and both the FAA and your insurer will read it that way after an incident. This is exactly the seam our chief pilot's team looks at during operator vetting, and it is why documents get re-reviewed every twelve months rather than filed once and forgotten.

Why the line blurs in the fourth quarter

Seasonality does more to create gray charter than bad intent does. From late September onward the calendar compresses: fall business travel, college football weekends, the Thanksgiving squeeze, then holidays and the opening of ski season. Demand concentrates on the same few days across the same few markets, and legitimate Part 135 supply in a given region simply runs out.

That is the moment an unusual offer appears. Someone knows a guy with a Citation sitting idle. A management company offers to "handle it privately" because their certificated fleet is committed. The price is attractive precisely because the operation skipped the expensive parts. In our experience the offer rarely arrives with a warning label on it. It arrives as a favor, from someone who sounds helpful, on the day you are out of options.

Peak season pricing has real causes, and we would rather explain them than watch someone route around them. What affects charter price walks through what is actually moving the number on a busy weekend. Booking earlier into those windows solves more than a bargain hunt does.

Five questions that settle it before you board

You do not need to audit anyone. You need five answers, and a legitimate operator or broker will produce them without friction.

1. Which company holds the Part 135 certificate for this flight, and what is its certificate number? Vague answers are the answer.
2. Is this specific tail number on that operator's operations specifications? An operator can be perfectly legitimate and still have an aircraft that is not listed on its certificate.
3. Who holds operational control? If the reply involves a lease, ask who is providing the crew. If the same party does both, stop.
4. Who are the two pilots, what are their hours in type, and are they current? Our own floor is two ATP rated pilots on every flight, published on our pilot standards page.
5. Can I see the certificate of insurance for this trip? A charter policy names the operation it covers. A Part 91 policy generally excludes commercial carriage, which means a gray charter passenger may be uninsured without knowing it.

Any operator running a real charter answers all five in one email. Hesitation on question one tends to make the other four unnecessary.

What this means for a normal booking

For most travelers the practical takeaway is short. Do not buy the flight, buy the operator. The badge conversation that follows, ARG/US, Wyvern, IS-BAO, only matters once the certificate question is settled, because a voluntary audit stacked on top of an uncertificated operation is decoration.

We approve a small fraction of the certificated operators in the United States and re-audit them annually, which is described filter by filter in how charter operator vetting actually works. If you want the shorter framing of the same subject, is flying private safe answers it in a page.

And if an offer lands in your inbox in November that does not fit any of this, send it to us. We will tell you what it is, even when the answer costs us the booking. That call is a good deal easier to make in advance than to explain afterward.