Flights conducted under part 121 or part 135 of this chapter

This regulation addresses when fractional ownership program flights must operate under the stricter Part 121 (airline) or Part 135 (commuter/on-demand) rules instead of the fractional ownership rules in Subpart K.

When a non-program aircraft substitutes for a scheduled program flight, it must operate under Part 121 or 135 rules (with one exception in §91.501(b)). Additionally, if a program manager holds a Part 119 certificate, they can conduct flights for fractional owners under Part 121 or 135, but only if that specific aircraft appears on their operations specifications for those parts.

Crucially, the regulation requires that fractional owners be informed which rules apply to their flight—whether it's operating as a normal program flight under Subpart K or under the more stringent Part 121/135 requirements. This transparency ensures owners understand the operational standards and crew requirements governing their specific flight.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*