Part 135 vs Part 91: Key Differences in Private Jet and Charter Flight Regulations

Definition and Purpose of Part 91 and Part 135

Part 91 and Part 135 are two categories of aviation operations defined by the FAA. In simple terms, Part 91 covers private general aviation flights, while Part 135 covers commercial charter flights and small commuter operations. They exist to differentiate non-commercial flying from for-hire commercial services, ensuring that paying passengers are protected by stricter safety rules.

Part 91 – Private (Non-Commercial) Aviation

A small private plane parked at a rural airfield, typical of general aviation operations under Part 91. Part 91 is the section of 14 CFR (Federal Aviation Regulations) that governs general operating and flight rules for civil aircraft. ​It applies to private aircraft flights that are not offering transportation for compensation. Think of a private pilot flying family or a company operating its own business jet for executives – these are Part 91 operations. Part 91 rules are relatively minimal and flexible for general aviation, covering basic safety and operating standards. Importantly, Part 91 essentially prohibits carrying paying passengers or cargo for hire except in very limited circumstances. This limitation is by design: it ensures that if money is involved, the flight must adhere to more stringent commercial standards under other parts (like Part 135 or the airline rules of Part 121). In short, Part 91 exists to regulate private flying and hobbyist or corporate operations, keeping them safe but without the full burden of commercial regulations.

Part 135 – Commercial Charter Operations

Part 135 is the set of FAA regulations for on-demand commercial operations, such as private charter flights, air taxi services, and small commuter airlines. It was created to hold commercial operators to a higher safety standard because the public is paying for transportation​. Part 135 covers commuter and charter aircraft with 30 or fewer passenger seats (and under 7,500 lbs payload) in non-scheduled service​. Think of the business jets, turboprops, or helicopters you can charter on a case-by-case basis – those flights operate under Part 135 rules. To legally fly passengers or cargo for profit under Part 135, an operator must obtain an FAA air carrier certificate (often called a “charter certificate”)​. This certification process is rigorous and time-consuming, reflecting the FAA’s view that commercial operators must be “especially careful” and accountable when transporting paying customers​. In essence, Part 135’s purpose is to provide a regulatory framework that ensures charter flights and other commercial small-scale operations maintain high levels of safety and oversight, above and beyond the baseline requirements of Part 91.

Legal and Regulatory Differences between Part 91 and Part 135

While both parts are under FAA regulations, there are significant legal differences in what is allowed and required. Here’s a breakdown of the primary differences in FAA rules governing Part 91 vs Part 135 operations:

• Commercial vs Private Use: Compensation is the dividing line. Under Part 91, you cannot hold out air transportation services or charge passengers (with only a few exceptions for cost-sharing or incidentals)​. Part 135, on the other hand, explicitly allows for-hire flights – it’s built for charter services and commercial air taxi operations. Any flight where passengers or cargo are transported for payment must be conducted under Part 135 (or another commercial part) to be legal.

• FAA Certification & Oversight: Part 135 operators must have an FAA-issued Operating Certificate (air carrier certificate) and approved Operations Specifications (Ops Specs) that detail how and where they can operate. ​The FAA closely oversees Part 135 companies, assigning them inspectors and requiring manuals, training programs, and regular audits. By contrast, Part 91 operations do not require a special certificate – a private owner or pilot can operate under Part 91 as long as they comply with the general rules. There’s far less direct FAA oversight on day-to-day Part 91 flights (no Ops Specs to adhere to), since these are considered private matters. Essentially, Part 135 is a permission slip to operate commercially, coming with considerable regulatory oversight, whereas Part 91 is the default set of rules for private flying.

• Safety Standards and Equipment: The safety regulations under Part 135 are more strict. For example, Part 135 mandates specific pilot training and proficiency checks, safety management protocols, and even requires crew drug and alcohol testing programs. Aircraft operated under Part 135 must be maintained to higher standards and sometimes carry additional equipment (such as fire-blocked interior materials or emergency gear) not required under Part 91​. ​Under Part 91, the safety burden is more on the pilot/owner’s judgment and basic compliance (e.g. following standard maintenance and operating rules). There are no FAA-mandated training or safety programs for private Part 91 flights beyond keeping the aircraft airworthy and the pilots legally current.

• Flight Operations Restrictions: Part 135 comes with more operational limitations designed for safety. For instance, weather minimums are stricter – a charter pilot cannot initiate an instrument approach to an airport if the reported weather is below landing minimums, whereas a Part 91 pilot could attempt it (legally) for practice or in hopes of improvement​. Part 135 flights generally cannot take off in zero-visibility conditions or use airports without official weather reporting for IFR operations​. . They also must account for additional runway safety margins (often requiring an extra 40% of runway length beyond what the aircraft performance needs)​. Part 91 operations are given more leeway to operate into short or unapproved fields and in marginal weather at the pilot’s discretion (though that doesn’t mean it’s always wise). Simply put, charter operations face tighter rules on when and where they can fly due to safety, whereas private flights have more freedom to operate as long as the pilot deems it safe.

• Security and Passenger Screening: Unlike airline travel, neither Part 91 nor Part 135 requires TSA airport security screening for passengers. However, Part 135 operators are required to verify passenger identification for anyone 18 or older on board​. If you charter a jet, expect to show a government ID before boarding, similar to an airline check (though you avoid the long security lines). In Part 91 private flights, there is no legal requirement for passenger IDs or background checks – you can bring along friends or colleagues on your own plane without formalities. The security protocols are essentially at the discretion of the aircraft owner/operator under Part 91, whereas Part 135 has mandated procedures to ensure everyone on a commercial charter is documented.

Operational Requirements: How Part 91 vs Part 135 Affect Flights

The differing rules in Part 91 and Part 135 lead to different operational requirements and standards. These affect everything from who can fly the plane to how it’s maintained and how long the crew can work. They even influence the onboard experience for passengers. Below we discuss how pilot qualifications, maintenance, crew duty limits, and passenger experience differ between Part 91 private operations and Part 135 charter operations.

Pilot Qualifications and Training

Under Part 91, a pilot only needs the appropriate pilot license and ratings for the aircraft to operate a flight. This could be a private pilot certificate for personal flights or a commercial certificate if operating someone else’s aircraft (without direct compensation). There is no additional Part 91-specific certification required to fly privately. Part 135, by contrast, requires more advanced qualifications. Pilots flying charter or commuter operations must hold at least a commercial pilot license with an instrument rating, and in many cases (especially for jet aircraft or serving as captain) they hold an Airline Transport Pilot (ATP) certificate). In fact, charter companies often set higher experience thresholds for their pilots. Additionally, Part 135 mandates structured training and regular proficiency checks. Charter pilots undergo initial and recurrent training programs approved by the FAA, and they must pass checkrides or flight tests on a regular schedule to remain current. Part 91 has no such requirement for formal recurrent training – a private pilot just needs to meet basic FAA currency rules (like a flight review every 24 months, and recent experience for carrying passengers or flying on instruments). The result is that Part 135 crews are held to professional training standards, while Part 91 pilots have more personal responsibility to keep themselves proficient. For passengers, this often means charter flights are operated by full-time professional pilots, whereas a Part 91 flight might be operated by an owner-pilot or an on-staff corporate pilot without the same frequent checkride requirements.

Aircraft Maintenance Standards

Maintenance is another area with stricter requirements under Part 135. Any aircraft on a Part 135 charter certificate must adhere to a rigorous maintenance program. This typically includes 100-hour inspections (if carrying passengers frequently), regular schedule of preventive maintenance, and compliance with all manufacturer recommended inspections – often overseen by the operator’s maintenance department and verified by the FAA. Part 135 aircraft may also need specific equipment upgrades or modifications to meet commercial standards (for example, additional emergency equipment, onboard radar for weather, terrain awareness systems, etc., depending on the operation). Under Part 91, the maintenance requirements are less intensive: privately operated planes must have an annual inspection (every 12 calendar months) and comply with any applicable Airworthiness Directives, but they don’t necessarily need the 100-hour inspection unless they’re used for training or hire. Part 91 owners can choose to maintain their aircraft to very high standards, but the law gives them more latitude – for instance, they can operate under minimum equipment rules with inoperative items (if allowed by FAR 91.213) without an FAA-approved Minimum Equipment List, unlike Part 135 which usually requires a formal MEL. In short, Part 135 demands a higher level of maintenance oversight to maximize safety and reliability​. Passengers on charter flights can take comfort that the aircraft’s upkeep is being closely monitored and must meet commercial reliability standards. On a private Part 91 flight, maintenance quality might vary by owner, since it’s self-regulated beyond the basic legal minimums.

Crew Duty Time Limits

One of the most significant operational differences is how long pilots and crew can work. Part 91 imposes no specific flight time or duty time limits on pilots (aside from the general mandate to avoid careless or reckless operation). In theory, a private pilot under Part 91 could fly all day and night with minimal rest – there is no legal requirement to stop, as long as they feel capable. Of course, fatigue rules in Part 91 are managed by common sense and self-discipline. By contrast, Part 135 has strict crew duty and rest rules to protect against fatigue. Charter pilots must adhere to regulated limits on how many hours they can fly in a day and how long their duty day can be (which includes flight planning and standby time). For example, a Part 135 pilot’s duty day might be limited to around 14 hours, with a maximum of 8 or 10 hours of actual flight time (depending on single or two-pilot crews), followed by a mandatory rest period (often at least 10 consecutive hours off) before the next duty period​. There are also cumulative limits (like total hours in any 7 consecutive days, etc.). Once a Part 135 crew hits their duty limit, the flight day is over – no exceptions without risking a violation. This means that if you charter a jet and your trip runs late, the crew might “time out” and be legally required to remain on the ground until they’ve had proper rest. Part 91 flights have greater flexibility – an owner pilot can decide to push on late into the night if they feel up to it, since the regulations don’t force a cut-off. However, the lack of legal limits in Part 91 doesn’t mean fatigue isn’t a concern; it simply means the pilot is entrusted to manage their own rest. The bottom line: Part 135’s duty limits add an extra layer of safety for passengers (ensuring your pilots are well-rested), whereas Part 91 relies on the pilot’s judgment and personal limits.

Passenger Experience and Onboard Procedures

From a passenger’s perspective, flying under Part 91 versus Part 135 can feel a bit different. Part 135 charter flights often operate much like a private mini-airline experience. The crew will conduct formal safety briefings before takeoff, covering seat belts, exits, life vests, etc., as required by FAA rules. The operator might provide in-flight amenities and a professional level of service (some charter operators even have flight attendants or catering on larger jets). You’ll also be asked for identification before boarding, and the charter company ensures weight and balance paperwork and other compliance items are in order behind the scenes. In contrast, a Part 91 private flight (say, riding in a friend’s plane or a company jet) is typically more informal and flexible. There’s no mandated safety briefing script (though a good pilot will still brief passengers for safety), and no ID checks or TSA-style procedures – you just show up at the general aviation terminal and go. The schedule can be very flexible; an owner can decide to delay departure on a whim or fly to an alternate airport without dealing with airline-like rules. The trade-off is that the oversight is all internal – you are relying on the pilot and aircraft owner to follow best practices. Another difference is that Part 135 flights must stick to their approved operating rules – for example, the pilot can’t take off overweight or land at an unapproved airstrip just because you asked; they have to follow the charter company’s manuals and FAA limitations. Part 91 flights, run by private individuals or companies, have more leeway to accommodate passenger requests (within the bounds of general safety and the aircraft’s capability). Overall, charter passengers under Part 135 will notice a more structured, safety-oriented experience, whereas Part 91 passengers may experience a more casual atmosphere. Both can be luxurious and comfortable – after all, a business jet cabin is the same regardless of part – but the behind-the-scenes rules differ in the name of safety and accountability.

Who Uses Each Type of Operation?

Another way to understand Part 91 vs Part 135 is to look at who typically flies under each set of rules. The type of operator and purpose of flight usually determines which part applies.

Part 91 Users – Private Owners and Corporations

Part 91 is used by those who are flying for private, non-commercial reasons. The most common Part 91 operators are private aircraft owners. For example, if you own a small Cessna or Cirrus and fly it for personal travel or recreation, you operate under Part 91. The same goes for families or individuals using their own private jets purely for personal or business use (not charters for the public). Corporate flight departments also fly under Part 91 – a company that owns an aircraft to transport its executives or employees is not selling seats to the public, so these flights are considered private operations. In these cases, even though professional pilots may be at the controls, the flights are not subject to Part 135 rules because the company isn’t charging passengers (the company is the operator for its own benefit). Other examples of Part 91 usage include flying clubs, hobbyist pilots, and flight training. (Training flights and certain aerial work like crop dusting or banner towing are allowed under Part 91, with some special provisions, since they’re not common carriage of passengers.) The key theme is that Part 91 flyers do not hold out a service to the general public – they are either flying themselves or invited guests, and any cost-sharing is tightly limited by regulation.

Part 135 Users – Charter Companies and Commercial Operators

Part 135 is used by operators who offer commercial air service on a small scale (non-airline). The prime example is a private charter company or “air taxi” service. These are businesses that you can call to book a private flight on their aircraft, usually charging by the hour or by the trip. When you hear about someone “chartering a private jet,” that flight is being conducted under Part 135 rules by a certified operator. Charter companies range from small outfits with one or two planes to large fleet operators serving many regions. Besides passenger charters, air ambulance services (medical evacuation flights), helicopter tour companies, and air cargo carriers with small aircraft often operate under Part 135. There is also a category of scheduled commuter airlines – typically those flying small planes (with ≤9 or 19 seats) on short regional routes – that use Part 135 if they don’t meet the criteria to be full Part 121 airlines. Essentially, any commercial operation that isn’t big enough to be an airline (Part 121) and involves aircraft within the size limits will fall under Part 135. Even some fractional ownership or jet-card programs may utilize Part 135 for flights when the aircraft are interchanged or made available for charter to others. Commercial charter operators choose Part 135 because it legally allows them to collect payment for flights, provided they comply with all the additional safety and paperwork requirements. If an operator tried to offer charter flights without a Part 135 certificate (i.e. operating illegally under Part 91), they would be in violation of FAA rules and could face serious penalties. Thus, reputable charter companies always operate under Part 135, and savvy passengers know to check that any flight for hire is being run by a Part 135 certified carrier.

To sum it up

In the world of private aviation, Part 91 and Part 135 operations each have their place. Part 91 rules allow private aircraft owners maximum freedom to fly on their own terms, while Part 135 provides a framework for charter services with legal requirements and safety standards enforced by the FAA​. Neither is “better” in absolute terms – they serve different needs. If you’re an aircraft owner flying yourself or your company team, Part 91 offers convenience and flexibility. If you’re a traveler looking to hire a private jet, Part 135 ensures your flight is conducted with commercial-level safety oversight. By understanding the differences – from definitions and regulations to operational impacts – you can make informed decisions and appreciate the careful balance the FAA has struck. Safe flying, whether under Part 91 or Part 135, ultimately comes down to respecting the rules and exercising good judgment. With this knowledge, you’ll be well-prepared the next time you climb aboard a private aircraft, knowing exactly what kind of operation it is and what that means for you.