Part 91 vs. Part 135: What the Difference Means After an Aviation Accident

Which Rules Governed the Flight You or Your Family Member Was On

The answer tells you which safety rules the operator was legally bound to follow on that flight, so it is usually the starting point.

Part 91 of Title 14 of the Code of Federal Regulations holds the general operating and flight rules for civil aircraft. Think of it as the floor. A weekend pilot taking a friend up, a corporate flight department moving its own staff, and a flight school lesson all start from Part 91. Every civil flight in the United States operates under at least Part 91.

Part 135 sits on top of that floor, and if you booked a charter, an air tour or an air ambulance, it is the layer most likely to matter. Its applicability section, 14 C.F.R. § 135.1, says it "prescribes rules governing" the "commuter or on-demand operations of each person who holds or is required to hold an Air Carrier Certificate or Operating Certificate under part 119." An on-demand operation is what most people call a charter or air taxi: a flight arranged when a customer wants it rather than on a published schedule. The section reaches further, including each person employed or used by the certificate holder, "including the maintenance, preventative maintenance and alteration of an aircraft"; "each person who is on board an aircraft being operated under this part"; commercial air tours; and "helicopter air ambulance operations." That last group means a passenger on board is within the part's reach. A Part 135 operator still follows Part 91 as well; the added layer does not replace the floor.

The line between the two usually comes down to the phrase "for compensation or hire." When someone is paid, directly or indirectly, to carry passengers or property, the flight generally moves out of purely private flying and into the certificated world. Whether a particular arrangement crossed that line is a question of fact, which is why how a trip was booked and paid for can matter as much as what the operator called it.

A third framework, Part 121, covers large air carriers flying scheduled airline service. Most private and charter accidents involve Part 91 or Part 135. Airline accidents and some cargo operations raise Part 121 questions, which the site's page on cargo plane crashes touches on.

What a Charter Operator Owed Passengers Beyond Private-Flight Rules

The first difference is the certificate itself. Section 135.1 ties Part 135 to anyone who "holds or is required to hold" an Air Carrier Certificate or Operating Certificate under Part 119. A private owner flying under Part 91 needs no operator certificate of that kind. A charter company carrying the public does. The word "required" matters to an injured passenger: the rule reaches an operator who should have held the certificate, not only one who did.

Beyond the certificate, Part 135 contains detailed rules on crew qualification and training, aircraft maintenance and inspection, limits on pilots' flight and duty time, and how the operator controls and supervises each flight. Each area leaves a paper trail that can later show what the operator did before the flight. Part 91 also addresses pilots and aircraft, but for private operations it is generally less prescriptive. The exact hours, ratings and inspection intervals depend on the aircraft, the type of operation and the operator's own approvals, so this page does not reduce them to a single number.

The idea tying these rules together is operational control: the certificate holder's authority over, and responsibility for, starting, conducting and ending each flight. In a charter, that responsibility sits with the company holding the certificate, not only with the pilot in the seat. The reach of § 135.1 to people "employed or used by a certificate holder," including those doing maintenance, reflects how widely that responsibility runs, and it means questions after a crash may extend beyond the pilot.

For a family member on a charter or air ambulance flight, these rules describe what the operator promised the government it would do before anyone boarded. In practical terms, the name of the operator, the ticket or charter agreement and any record of who was paid tend to be the first documents that show whether this layer applied. The site's pages on charter flight crashes and medical helicopter crashes look at those operations more closely.

Why the Applicable Part Matters When Someone Is Hurt

In a negligence claim, the injured person generally has to show a duty, a breach of that duty, causation and damages. The duty is often called the standard of care: what a reasonably careful operator in the same position would have done. Federal aviation rules frequently serve as evidence of that standard. A Part 135 operator's duties are written out in more detail, so the question of whether it met them can be more specific than for a private flight.

That is why Part 135 records can carry weight. An operator working under a certificate generally keeps documents tied to it: the certificate and its approvals, pilot training and qualification records, maintenance records, and flight and duty-time records. What those records show, and what they leave out, can help explain what happened. Whether any of them shows a breach depends on the facts.

A harder question sometimes arises. A flight may be described as private, a Part 91 trip, when in substance someone was paid to provide it. If so, the Part 135 rules may have applied all along, even though no one followed them. Courts treat this as a mixed question of fact and law: who paid, what was promised, who controlled the aircraft. The answer can change which standards apply, so the label someone put on a flight is not the last word. The site's page on private jet crashes discusses how the line appears in business aviation.

The government's investigation runs on its own track. The National Transportation Safety Board (NTSB), the independent federal agency that investigates civil aviation accidents, is separate from any civil case. Under 49 U.S.C. § 1154(b), "No part of a report of the Board, related to an accident or an investigation of an accident, may be admitted into evidence or used in a civil action for damages resulting from a matter mentioned in the report." The operator's own regulatory record is a different layer of evidence, covered below.

How State Tort Law Overlays the Federal Regulatory Framework

The federal rules set safety standards. In general, though, the claim an injured passenger or a family brings is a state-law claim: negligence, wrongful death (a claim by certain family members or a representative after a death caused by another's wrongful act) or product liability. Federal regulations usually come into these cases as evidence of what care was required, not as a separate federal lawsuit replacing the state claim.

State law is not uniform. Limitation periods, the deadlines for filing suit, differ from state to state, as do when they start to run and their exceptions. Fault rules differ too. Some states reduce recovery by the injured person's share of fault; others bar recovery once that share passes a certain line. Wrongful-death statutes vary in who may bring the claim and what damages the law allows. State-specific pages on this site, such as the one for a Texas aviation accident lawyer, set out one state's rules from its own statutes.

Which state's law governs is its own question. The place of the crash, where the flight began, where the operator is based and where the injured person lives can all bear on it. Some deaths fall under federal law instead. The Death on the High Seas Act, named in 46 U.S.C. § 30301, is a federal statute for certain deaths on the high seas. Whether it reaches a particular over-water crash depends on where and how the death occurred.

Product liability is a separate theory from operator negligence. It asks whether an aircraft, an engine, avionics or another component was defective and whether that defect caused the harm. A crash does not prove a defect, any more than it proves the operator was careless. Both questions turn on evidence. Federal preemption issues can also arise in particular settings, and they are specific to the facts of each case.

What Investigators and Attorneys Look at After a Charter or Private Flight Accident

The NTSB's work usually unfolds in stages. A preliminary report is an early summary of basic facts, not a finding of why the accident happened. Factual information gathered during the investigation follows. A probable cause is the NTSB's final statement of what it determined most likely caused the accident; while an investigation is open, none has been stated. The bar in § 1154(b), set out above, keeps the Board's reports out of a civil damages case.

The same statute limits recordings. Under § 1154(a), a party generally may not use discovery to obtain a cockpit recorder recording, or parts of a transcript or still images the NTSB has not made public. A court may allow it only after a private review, called an in camera review, and only if what is public is not enough for a fair trial. Then it issues a protective order limiting use of the material to the case.

The regulatory record is a different matter. When Part 135 compliance is at issue, the records that tend to matter include:

• the operator's FAA certificate and the approvals tied to it
• the pilots' certificates and training records
• the aircraft's maintenance logs and inspection history
• flight, duty-time and rest records
• flight manifests and passenger lists
• documents showing who held operational control of the flight

FAA enforcement records and airworthiness directives, which are mandatory safety orders for specific aircraft or parts, can be further public sources. Physical evidence matters too: the wreckage, and flight data or cockpit voice recorder data where the aircraft carried them.

On the injured person's or family's side, the records that usually matter include medical records, photographs and video from the scene or the trip, the ticket, invoice or charter agreement, messages about how the flight was booked and paid for, incident reports, and the names of witnesses. Many of these are already in a family's hands, and the booking and payment records often bear directly on whether a flight was truly private.

Questions Worth Asking Before Deciding How to Proceed

The questions below shape which rules applied, what evidence exists and which state's law governs. None has a stock answer.

Was the flight conducted under Part 135 or Part 91, and do the facts support that label? Who paid, and to whom? Did the operator hold the certificate § 135.1 describes when the accident happened, or was it required to hold one and did not? Did the pilot meet the qualification and training requirements for that kind of operation?

What does the maintenance history show about the aircraft's condition? Is the NTSB investigation open or closed, and what has the Board itself stated so far? Is there any sign that a component or system failed, which could raise a product liability question alongside any claim against the operator?

Then come the state-law questions. Which state's law governs? What limitation period applies under that state's statute, when does it begin to run, and what exceptions does it contain? Do any wrongful-death rules or federal statutes apply instead? A family weighing these questions after a crash is often doing it while grieving, and working through them one at a time can make the situation easier to hold.

A conversation with an attorney can help sort out which rules governed the flight, which records bear on that, and how federal and state law fit together. A case evaluation is available for those who want one. The site's aviation accident lawyer page covers how these claims work more broadly.