Who Controls the Flight Decides the Rules: U.S. Part 135 vs Part 91

Part 91 governs private, non-commercial flying, while Part 135 covers on-demand commercial charter operations conducted for compensation or hire. The practical trigger is simple: if payment changes hands for the flight or an operator controls the scheduling and crew, Part 135 requirements generally apply. Edge cases exist, so check 14 CFR and FAA guidance before assuming either category fits your situation.

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TL;DR:

• If payment is involved or the operator controls scheduling, the flight likely falls under Part 135, requiring certification and stricter operational controls.
• Part 135 pilots need at least 1,200 total flight hours, including specific cross-country, night, and instrument hours, unlike Part 91 pilots who only need the required license and ratings.
• Operating under Part 135 requires adherence to mandated duty, rest, and drug testing rules, while Part 91 private flights generally do not, impacting crew fatigue management and safety standards.
• Transitioning from Part 91 to Part 135 involves comprehensive maintenance record audits, pilot qualification checks, and developing an approved Operations Manual and drug testing program.
• Certification restrictions affect day-to-day operations by imposing runway length margins, weather minimums, and TSA security protocols, especially at busy regional airports.

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Table of Contents

• Key differences at a glance
• Regulatory requirements: certification, pilot qualifications, duty and rest, and drug testing
• Maintenance, inspections, and airworthiness differences
• Operational control and common legal tests
• Operational limitations that change whether and where you can fly
• How to decide which is right for your flight
• Transition checklist: moving an operation from Part 91 to Part 135
• A regional operator’s perspective on Part 135 compliance
• FAQ
• Sources

Key differences at a glance

Before digging into the regulatory detail, here is a scannable comparison of what actually changes between the two parts.

• Certification: Part 135 operators need an FAA Air Carrier Certificate and approved Operations Specifications; Part 91 operators need neither.
• Pilot minimums: Part 135 sets specific hour requirements for IFR passenger-carrying pilots in command, while Part 91 relies on baseline certificate and rating requirements.
• Duty, rest, and drug testing: Part 135 mandates formal duty and rest limits plus a drug and alcohol testing program; most Part 91 flights carry no such mandate.
• Maintenance and inspections: Part 135 aircraft typically operate under an approved inspection program with minimum equipment list provisions; Part 91 maintenance is more flexible.
• Operational control: Whoever schedules the flight, hires the pilot, and directs the operation determines which part applies, regardless of who owns the aircraft.
• Airport access and security: Runway performance rules, weather minimums, and TSA security programs can restrict where and how a Part 135 flight operates.

Regulatory requirements: certification, pilot qualifications, duty and rest, and drug testing

Operating under Part 135 starts with an Air Carrier Certificate, which requires submitting an application, an Operations Manual, and a set of Operations Specifications (OpSpecs) to the FAA. The OpSpecs spell out exactly what aircraft, routes, and operations the certificate holder is authorized to fly, and the application process typically runs through a Flight Standards District Office before any revenue flight takes place.

Pilot qualifications tighten considerably under Part 135. A pilot in command flying IFR passenger-carrying operations under Part 135 needs 1,200 total flight hours, including 500 cross-country hours, 100 night hours, and 75 instrument hours. Part 91 imposes no comparable hour floor: a private pilot can fly with only the certificate and ratings required for the specific flight, with no minimum total time tied to passenger carriage.

Duty time and rest rules follow the same pattern. Part 135 crewmembers operate under defined flight-time limitations and mandatory rest periods designed to manage fatigue across a duty day, something Part 91 private flights are not required to track or enforce. A charter pilot flying several legs in a single day has hard limits on how many hours they can be on duty and how much rest must follow, while a Part 91 pilot flying the same route pattern privately faces no such ceiling.

Drug and alcohol testing is another firm line between the two parts. Part 135 operators must run a full testing program covering random testing, pre-employment screening, post-accident testing, reasonable-suspicion testing, and return-to-duty testing after a violation. These categories exist specifically because Part 135 pilots are carrying paying passengers or cargo, and the FAA treats that commercial relationship as justification for ongoing safety verification that private Part 91 flying does not require.

Taken together, these rules mean a Part 135 certificate holder carries continuous compliance obligations, not a one-time application. Training, testing, and recordkeeping run on an ongoing cycle, and ACT ARC Recommendation 25-5 illustrates that the FAA is still refining guidance around specific pieces of that cycle, including how certificate holders contract check pilot services for training and competency checks.

Maintenance, inspections, and airworthiness differences

Part 91 gives aircraft owners real flexibility: maintenance can follow the manufacturer’s recommended schedule, an owner-selected program, or the minimums in 14 CFR Part 91 Subpart E, with fewer mandatory inspection intervals. Part 135 operations typically require an FAA-approved continuous airworthiness maintenance program, and many of the standard Part 91 maintenance provisions no longer apply once an aircraft is maintained under that approved program instead.

A Minimum Equipment List becomes relevant for Part 135 operators in a way it rarely does under Part 91, since the MEL defines exactly which equipment can be inoperative while still permitting a legal, safe departure. That distinction affects aircraft availability directly: a Part 135 aircraft with an inoperative item outside MEL allowances is grounded until repaired, while a Part 91 owner has more latitude to make a judgment call.

Records and audit expectations shift as well. Commercial operations draw closer FAA scrutiny, and maintenance documentation needs to be complete, current, and traceable. Operators moving an aircraft from private to commercial use often discover gaps in logbooks or inspection records that never mattered under Part 91 but become a real obstacle during a Part 135 certification review.

These differences carry cost consequences. Approved inspection programs, MEL compliance, and tighter recordkeeping add overhead that private owners rarely budget for, and insurers price Part 135 operations differently given the commercial exposure and passenger-carrying liability involved.

Operational control and common legal tests

The FAA decides which part applies based on operational control, meaning who actually directs a flight rather than who owns the airplane. Inspectors and legal interpretations look at who dispatches the flight, who hires and pays the pilot, who sets the schedule, and who is responsible for maintenance decisions. FAA legal interpretations make clear that paperwork alone does not settle the question: a contract that names the aircraft owner as “in control” does not protect an arrangement if, in practice, someone else is calling the operational shots.

A wet lease, where one party provides both the aircraft and the crew to another party, is treated as strong evidence of a Part 135 operation. Combining airplane and pilot from the same source looks like a commercial charter arrangement even when the parties label it otherwise, and FAA enforcement materials confirm that inspectors weigh actual operational decisions over contract language when sorting out these cases.

Three common scenarios illustrate how this plays out:

1. A company owns an aircraft and hires a management firm that also supplies the pilots and handles all scheduling: this combined aircraft-and-crew arrangement typically points toward Part 135.
2. A fractional ownership program sells shares of an aircraft but the program operator schedules flights and assigns crew across all owners: this structure often requires Part 135 certification for the managing entity.
3. An individual owner flies their own aircraft with their own employed pilot, with no compensation changing hands for the flight itself: this generally stays under Part 91.

Operational limitations that change whether and where you can fly

Part 135 certification brings restrictions that reach beyond paperwork and into day-to-day flight planning. One of the most consequential is the landing distance rule: Part 135 turbojet operations must be able to land within 80% of the available runway length at the destination, accounting for conditions at arrival. That margin rules out some shorter regional runways that a Part 91 flight could use without issue.

Weather and approach minimums diverge as well. Part 135 operators generally cannot begin an instrument approach at an airport without a weather reporting source confirming conditions are at or above minimums, a restriction that does not apply the same way to Part 91 flying.

TSA security programs add another layer for certain Part 135 operators above specific aircraft weight thresholds, requiring passenger list verification and criminal-history record checks. For charter operators, that means last-minute passenger changes can trigger additional screening steps that a private Part 91 flight would never encounter.

How to decide which is right for your flight

Working through a short checklist clarifies which rules actually apply to a given flight or operation.

1. Will any compensation change hands for the flight? If yes, Part 135 is the likely framework regardless of who owns the aircraft.
2. Who controls scheduling and crew assignment? If a third party dispatches the flight and supplies the pilot, that points toward Part 135.
3. How frequently will flights occur, and will they carry different paying passengers? Regular commercial service strengthens the case for Part 135 certification.
4. What access to smaller regional airports do you need? Part 135’s runway and weather restrictions may rule out airports a private Part 91 flight could use.

Before contracting with any operator, ask directly who exercises operational control, what maintenance program the aircraft follows, what hour minimums the pilots meet, whether a drug-testing program is in place, and what insurance coverage applies to passengers. The tradeoff runs in both directions: Part 135 adds cost and operational limits, but it also shifts legal and safety responsibility onto a certificated operator rather than leaving it with an individual owner.

Pro Tip: Ask any charter operator for their Air Carrier Certificate number and OpSpecs summary before booking: a legitimate Part 135 operator will provide both without hesitation.

Transition checklist: moving an operation from Part 91 to Part 135

Operators planning to shift an aircraft into commercial service face a defined set of steps.

• Audit maintenance records for gaps, since transitioning to Part 135 commonly surfaces documentation issues that never mattered under Part 91.
• Confirm every pilot in command meets the Part 135 IFR passenger-carrying hour minimums before scheduling revenue flights.
• Draft an Operations Manual and prepare the specific OpSpecs requests the certificate will need.
• Stand up a drug and alcohol testing program covering all required testing categories.
• Finalize insurance coverage and TSA security steps if the aircraft falls above the relevant weight threshold.
• Schedule meetings with your FAA Principal Operations Inspector early, since certificate review timelines often run longer than operators expect.

Maintenance record cleanup and pilot qualification verification tend to take the longest and drive the bulk of transition cost, so starting those two items first shortens the overall timeline.

A regional operator’s perspective on Part 135 compliance

Operating on-demand whole-airplane charters between regional airports means Part 135 compliance shapes nearly every part of the experience we build for passengers. Our Cirrus fleet, equipped with the Cirrus Airframe Parachute System, reflects a safety posture that complements the standardized pilot training Part 135 requires. Compliance costs show up in scheduling discipline and transparent, fixed pricing rather than hidden fees, which is part of why Littlebird prices each regional charter upfront before booking.

— Nick

FAQ

Can a pilot over 65 fly Part 135?

Age limits for commercial pilots are governed by Part 61 and, for certain international operations, ICAO-aligned standards rather than a blanket Part 135 cutoff. There is no universal age restriction for domestic Part 135 flying, so the applicable limit depends on the specific operation and any international segments involved.

What’s the hardest pilot license to get?

Difficulty is subjective, but the Airline Transport Pilot certificate is widely considered the most demanding to earn because it requires extensive flight experience, advanced knowledge testing, and a rigorous practical exam. Part 135 operations often require pilots who hold this certificate or meet comparable experience thresholds for IFR passenger-carrying flights.

Can a pilot flying Part 91 be paid for flying?

A pilot can be paid as an employee to fly an aircraft under Part 91, but charging passengers or shippers for the flight itself generally pushes the operation into Part 135 territory. The distinction rests on whether compensation is tied to the transportation service rather than simply to piloting duties.

Is NetJets Part 135 or Part 91?

Fractional ownership programs typically involve both parts depending on the specific flight and who exercises operational control at that moment. The managing company that schedules flights and supplies crew across fractional owners commonly operates under Part 135 certification for those flights.

Sources

• FAA — Crewmember flight, duty, and rest requirements (FAQ)
• eCFR / 14 CFR § 135.243 — Pilot in command requirements
• Comparison of Part 91 versus Part 135 — MidwestFlyer