Applicability

This regulation defines which aircraft and operations must follow the maintenance rules in Subpart E of Part 91. It applies to all U.S.-registered civil aircraft, whether flying domestically or internationally.

However, certain aircraft are exempt from some of these maintenance requirements. If your aircraft operates under a continuous airworthiness maintenance program (such as those used by airlines under Part 121 or 135, or certain international operators), you don't need to follow sections 91.405, 91.409, 91.411, 91.417, and 91.419. Similarly, airplanes inspected under Part 125 rules are exempt from sections 91.405 and 91.409.

In practical terms, this means most general aviation pilots must comply with all the maintenance requirements in this subpart, while aircraft operating under more comprehensive commercial maintenance programs follow their own specific rules instead. This prevents duplicate or conflicting maintenance requirements for commercial operators.

*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.*