Part 91K (Fractional Operations)
Part 91 Subpart K ("Part 91K") is the FAA regulation governing fractional aircraft ownership programs. It's a subset of Part 91 (non-commercial) that adds program-specific crew currency, maintenance, and operational-control requirements.
Also known as: 14 cfr part 91 subpart k, part 91 subpart k, fractional regulation
Part 91K was finalized in 2003 to resolve a long-running ambiguity about whether fractional programs were commercial (Part 135) or non-commercial (Part 91). The compromise: fractional programs operate under Part 91 — preserving the favorable tax and operational treatment — but with additional Part-135-style oversight on crew duty, training, and maintenance under the K subpart.
NetJets, Flexjet, FlexAir, PlaneSense, and most other major fractional programs operate under Part 91K. Some smaller fractional and shared-ownership models operate under Part 135 instead, which changes their tax treatment, insurance, and operational control. The customer-facing product is roughly equivalent either way.
Part 91K and Part 135 are functionally similar from a safety-oversight perspective. The practical difference for buyers is in pricing and tax treatment — Part 91K programs are not subject to the 7.5% FET on flight-time charges (though they are on some ancillary services), which is part of why fractional per-hour rates can be competitive against on-demand charter for high-volume users.
Frequently asked questions
- What's the difference between Part 91K and Part 135?
- Part 91K is for fractional ownership programs (NetJets, Flexjet, etc.) — operates under Part 91 with additional fractional-specific requirements on crew, training, and maintenance. Part 135 is for on-demand commercial charter — required in the United States for any paid charter, including empty legs.
Related terms
- Fractional Ownership
Fractional jet ownership programs sell shares of an aircraft to multiple owners, who each get an annual flight allowance and pay a monthly management fee. Programs like NetJets, Flexjet, and PlaneSense compete with empty legs by trading higher predictability for higher cost.
- Part 91 (Private Operations)
Part 91 of the FAA regulations governs non-commercial flight operations — private owners flying their own aircraft, corporate flight departments flying company aircraft, recreational pilots. Aircraft on Part 91 cannot be chartered for hire; doing so anyway is illegal "gray" charter.
- Part 135 Operator
A Part 135 operator is an FAA-certificated company authorized to fly paying passengers on private (non-scheduled) charter aircraft under 14 CFR Part 135. Every legitimate private jet charter flown in the United States — including every empty leg — is operated under a Part 135 certificate; operators based elsewhere fly under the equivalent authority in their own jurisdiction.
- Federal Excise Tax (FET)
The Federal Excise Tax (FET) is a 7.5% federal tax on the price of domestic commercial air transportation, including private jet charter and empty leg flights. The tax is collected by the operator and remitted to the IRS; it appears on every empty-leg booking confirmation.
Sources
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