The Regulation Interviewers Use to Test Your Judgment
FAR 91.403 is deceptively short. It reads: "The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with this chapter and with airworthiness directives under part 39 of this chapter."
Two sentences. High stakes. Interviewers at major and regional carriers use this reg to probe whether you understand where the accountability chain actually starts — and whether you've internalized what "airworthy" means operationally, not just academically.
What 91.403 Actually Establishes
The regulation places primary maintenance responsibility on the owner or operator, not the mechanic who signed off the logbook. This is the foundational principle of Part 91 maintenance — everything else in Subpart E flows from it.
- 91.403(a) — Owner/operator is primarily responsible for airworthiness, including AD compliance
- 91.403(b) — No one may perform maintenance or alterations except as prescribed in Subpart E
- 91.403(c) — When a manufacturer's ICA (Instructions for Continued Airworthiness) contains an Airworthiness Limitations section, those mandatory replacement times and inspection intervals must be followed
The word "primarily" is deliberate. It doesn't absolve the PIC — 91.7 separately requires you to verify airworthiness before flight. But 91.403 makes clear that the party responsible for keeping the aircraft in a condition worth flying is the operator, not the maintenance provider.
How This Appears in Airline Interviews
Interviewers rarely ask you to recite 91.403 verbatim. They probe its implications through scenario questions.
"You arrive at the aircraft and the maintenance log shows an open writeup — the APU won't start. The mechanic tells you it's been deferred. Who is ultimately responsible for whether this aircraft is airworthy for today's flight?"
The correct answer framework: the operator holds primary responsibility under 91.403, the operator's ops specs and MEL govern whether the deferral is legal, and you as PIC bear final authority and responsibility before accepting the aircraft under 91.7. A deferred item isn't automatically airworthy — it's legal to operate with if the MEL permits it, which is a separate question.
Strong candidates connect the dots: 91.403 → operator accountability → MEL authorization under 91.213 → PIC airworthiness determination under 91.7. That chain of reasoning signals systems-level thinking, which is exactly what chief pilots want to see.
"The item is on the MEL with a 10-day deferral, but the original writeup was made 9 days ago. What do you do?"
This tests whether you understand that MEL intervals are calendar-based, that your operator's maintenance control or dispatch needs to resolve it before departure, and that you do not dispatch with an expired deferral regardless of external pressure.
The ICA and Airworthiness Limitations Piece
91.403(c) surfaces less often in interview rooms but trips up candidates who haven't thought through type-specific maintenance. When a manufacturer issues ICAs — mandatory for transport-category aircraft — any airworthiness limitations sections carry the force of a continuous AD. You can't negotiate or defer them.
If you're transitioning to a new type and your interview covers maintenance knowledge, know whether your target aircraft has life-limited parts or structural inspection thresholds in its ICA. Interviewers at carriers operating aging fleets — think regional operators with high-cycle narrowbodies — may go here specifically.
For operator-specific maintenance question sets, including what United, Delta, and regional carriers have asked about airworthiness and MEL scenarios in recent hiring cycles, the Vectors to Hired question bank pulls from verified pilot gouge across United, SkyWest, and 53 other operators.
The Takeaway for Interview Prep
When you see a 91.403 question, the interviewer is testing three things: whether you know who owns the accountability, whether you understand the PIC's independent obligation under 91.7, and whether you can apply both in a pressure scenario without caving to an imaginary captain or dispatcher pushing you to go.
Treat regulations not as isolated rules to memorize but as a framework for decision-making. That's the answer style that earns fours and fives on a scoring rubric — and the interview panel's confidence that you'll handle the real thing the same way.
Practice your reg knowledge out loud using the AI Voice Coach before your interview. Reading regs is not the same as being able to explain them clearly under pressure.