FAR 91.403 — Maintenance Responsibility
FAR 91.403 makes the owner/operator primarily responsible for keeping an aircraft airworthy. Learn what it means for pilots, ADs, and STCs.
In Plain English
FAR 91.403 establishes who is responsible for keeping an aircraft airworthy and the rules around performing maintenance on it. As a pilot, this is one of the most cited regs on checkrides because it ties directly to your preflight airworthiness determination.
Key points of the rule:
- The owner or operator is primarily responsible for maintaining the aircraft in an airworthy condition, including compliance with Part 39 (Airworthiness Directives).
- Maintenance, preventive maintenance, and alterations may only be performed as prescribed in Subpart E of Part 91 and other applicable rules, including Part 43.
- If the manufacturer's maintenance manual or Instructions for Continued Airworthiness contains an Airworthiness Limitations Section, the mandatory replacement times, inspection intervals, and related procedures must be complied with (or approved alternatives under Part 121/135 ops specs or §91.409(e)).
- An aircraft cannot be altered under a Supplemental Type Certificate (STC) unless the owner/operator holds that STC or has written permission from the holder.
Operationally, this means the owner/operator — not the mechanic — bears ultimate responsibility for ADs, inspections, and life-limited parts.
Regulation Text
14 CFR § 91.403§ 91.403 General.
(a) The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter.
(b) No person may perform maintenance, preventive maintenance, or alterations on an aircraft other than as prescribed in this subpart and other applicable regulations, including part 43 of this chapter.
(c) No person may operate an aircraft for which a manufacturer's maintenance manual or instructions for continued airworthiness has been issued that contains an airworthiness limitations section unless the mandatory replacement times, inspection intervals, and related procedures specified in that section or alternative inspection intervals and related procedures set forth in an operations specification approved by the Administrator under part 121 or 135 of this chapter or in accordance with an inspection program approved under § 91.409(e) have been complied with.
(d) A person must not alter an aircraft based on a supplemental type certificate unless the owner or operator of the aircraft is the holder of the supplemental type certificate, or has written permission from the holder.
[Docket 18334, 54 FR 34311, Aug. 18, 1989, as amended by Amdt. 91-267, 66 FR 21066, Apr. 27, 2001; Amdt. 91-293, 71 FR 56005, Sept. 26, 2006]
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Oral Exam Questions a DPE Might Ask
Q1Who is primarily responsible for keeping an aircraft in an airworthy condition?
Per FAR 91.403(a), the owner or operator of the aircraft is primarily responsible for maintaining it in an airworthy condition, including compliance with Part 39 Airworthiness Directives.
Q2Can you legally alter your aircraft using someone else's Supplemental Type Certificate?
Only if you hold the STC yourself or have written permission from the STC holder, as required by FAR 91.403(d).
Q3What must be complied with if the manufacturer's maintenance manual includes an Airworthiness Limitations Section?
FAR 91.403(c) requires compliance with the mandatory replacement times, inspection intervals, and related procedures in that section, unless approved alternatives under Part 121/135 ops specs or an inspection program under §91.409(e) are used.
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