Applicability

This regulation establishes which maintenance rules apply to Part 135 operators based on aircraft size.

For smaller aircraft (9 passenger seats or less): You follow the standard Part 91 and Part 43 maintenance rules, plus four specific Part 135 sections (135.415, 135.417, 135.421, and 135.422). You may optionally use an approved aircraft inspection program under 135.419.

For larger aircraft (10+ passenger seats): You must follow a more comprehensive Part 135 maintenance program detailed in sections 135.415 through 135.443.

Special cases: Any operator with smaller aircraft can voluntarily choose to follow the more rigorous large-aircraft maintenance program. Single-engine aircraft used for passenger IFR operations have additional requirements. Operators conducting commuter operations under §135.364 must use the large-aircraft program plus additional Appendix G requirements.

This matters because it determines your inspection intervals, required programs, and recordkeeping obligations—larger aircraft face stricter oversight.

*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.*