Part 91 and Part 135 Operations: Flight Department and Charter Standards
Many aviation matters turn on a question that sits upstream of the accident itself: how was the operation run? A corporate flight department operating under 14 CFR Part 91 and a charter operator certificated under 14 CFR Part 135 can fly the same aircraft type over the same route, yet the regulatory framework, the lines of responsibility, and the records each one should produce are very different. Understanding that difference is often the first step in a credible operational review, and it is the area where an aviation expert witness with current flight department experience can add the most clarity.
I am an ATP-rated Chief Pilot based in Tampa, Florida, with more than 5,000 flight hours and international corporate aviation experience. I lead a Part 91 corporate flight department, which means the questions in this area are the same ones I work through in my own operation: who has authority to accept or decline a trip, how crews are scheduled and rested, how aircraft limitations are checked against the mission, and how the organization knows its procedures are being followed.
What Distinguishes the Two Frameworks
Part 91 sets the general operating and flight rules for all civil aircraft. For a corporate flight department carrying company personnel, those rules are the regulatory floor. Under 14 CFR 91.3, the pilot in command is directly responsible for, and is the final authority as to, the operation of the aircraft. Under 14 CFR 91.103, the pilot must become familiar with all available information concerning the flight before departure. Beyond those requirements, the standard for a well-run Part 91 department usually comes from its own operations manual, its training program, manufacturer guidance, and voluntary programs such as the International Standard for Business Aircraft Operations (IS-BAO) or a safety management system modeled on 14 CFR Part 5.
Part 135 adds a layer of certificate-holder responsibility. The operator must maintain an approved manual, conduct training and checking under Subparts G and H, comply with flight, duty, and rest limits, and exercise operational control, which 14 CFR 1.1 defines as the exercise of authority over initiating, conducting, or terminating a flight. When a Part 135 flight goes wrong, the analysis rarely stops at the cockpit. It extends to the people who dispatched the flight, the procedures that governed loading and weather decisions, and the oversight that should have identified recurring problems.
The line between the two is not always obvious. Whether a flight was properly conducted under Part 91 or should have been conducted under Part 135 depends on the specific facts: who paid, who was carried, and who held operational control. Characterizing an operation before the records establish it would be premature. That determination begins with documents, not assumptions.
How an Operational Review Approaches These Matters
A sound review moves from the flight itself to the organization around it. It starts with flight planning and preflight decisions, then examines aircraft performance and weight-and-balance, crew qualification and currency, flight, duty, and rest records, and finally the manuals, training programs, and oversight practices that shaped those decisions. Regulatory minimums are treated as floors. The more useful question is usually how the operator's own procedures compared with established practice in comparable operations, and whether those procedures were followed in practice or only on paper.
Documented facts are kept separate from assumptions, and each opinion is tied to a source that can be explained and independently evaluated. Where an NTSB investigation exists, its findings provide the investigative foundation for that work.
Records Worth Examining
Operations manuals and general operations manual (GOM) revisions in effect on the date of the flight, trip sheets and flight release documentation, load manifests and weight-and-balance computations, crew training and checking records, duty and rest logs, maintenance and minimum equipment list (MEL) records, safety reports, and internal audit findings all help reconstruct how an operation actually functioned. Whether and how those materials are obtained is a matter for counsel.
Frequently Asked Questions
Is a Part 91 corporate flight department held to a lower standard than a Part 135 operator?
The regulatory requirements are different, and Part 91 imposes fewer of them. But a well-run Part 91 department typically operates to its own manual, training standards, and safety program, and those documents help define what established practice looked like for that operation.
What does operational control mean in a Part 135 matter?
Under 14 CFR 1.1, it is the exercise of authority over initiating, conducting, or terminating a flight. An operational review examines who held that authority, how it was exercised, and whether the certificate holder's procedures supported sound decisions.
Can an aviation expert determine whether a flight should have been conducted under Part 135?
An operational review can lay out the facts that bear on that question, such as who held operational control and how the flight was arranged. How those facts apply legally is a question for counsel.
Discuss a Part 91 or Part 135 Matter
If a matter involves a corporate flight department, a charter operator, or a question about how an operation was structured and overseen, an early independent review can clarify which records matter and what operational questions they need to answer. Learn more about AeroVerdict's aviation expert witness services.