FAR 117 vs 121.467 Duty Limits Explained

On a Part 121 airline flight, the pilots and the flight attendants are subject to two different sets of duty and rest rules. The flight crew falls under FAR 117 (14 CFR Part 117); the cabin crew falls under 14 CFR 121.467. They share the same purpose — preventing fatigue-related risk — but they are not the same rule, and treating them as interchangeable is how an airline ends up with a crew-legality error nobody caught until after the line was built.

Two regimes, one airplane

FAR 117 was a significant modernization of pilot fatigue rules: it ties limits to the science of fatigue, accounting for time of day, the number of flight segments, and the start time of the duty period, with cumulative limits over rolling windows. 121.467, the flight-attendant rule, predates 117's framework and is structured more simply around scheduled duty periods and required rest. Because the two were written in different eras around different assumptions, the numbers and the way they're calculated diverge — which is exactly why the same trip can be legal for one crew group and not the other.

How FAR 117 works (pilots)

FAR 117 governs flight time, flight duty period (FDP), and rest for Part 121 flightcrew members. The maximum FDP isn't a single number — it varies with when the duty period starts and how many flight segments it contains, reflecting that a duty period starting at an unfavorable circadian time, or with many legs, is more fatiguing. On top of the per-duty-period FDP limits, 117 imposes flight-time limits and cumulative limits across rolling periods, plus minimum rest requirements before a duty period. The practical effect: legality has to be evaluated against the specific pairing, not a flat daily cap.

How 121.467 works (flight attendants)

14 CFR 121.467 sets duty-period limits and required rest for flight attendants. Its structure centers on the scheduled duty period and the rest that must follow, with provisions that allow longer duty when augmented rest is provided. It does not use FAR 117's segment-and-start-time FDP table. So a cabin crew's legality is computed on its own terms — and a pairing that's fine for the flight deck under 117 might need a different look for the cabin under 121.467, or vice versa.

Deterministic, not predictive

Both 117 and 121.467 are rule sets with defined inputs and defined outputs — a given duty period either fits the limits or it doesn't. Good enforcement is therefore deterministic and explainable: feed in the pairing and the rule tells you yes or no, and you can trace why. That's different from fatigue-risk scoring, which blends documented duty load with self-reported sleep into a risk view to help prioritize attention. The two are complementary, but only the regulatory limits are pass/fail — fatigue scoring is an aid, not a legality check.

The takeaway

Pilots and flight attendants on the same Part 121 flight follow parallel but distinct duty/rest rules. Build (or buy) crew tooling that enforces FAR 117 for the flight deck and 121.467 for the cabin, each at assignment time, and you close the most common crew-legality gap before it becomes a finding. For the exact limits and edge cases, work from the current regulatory text and your carrier's Ops Specs — the rules contain nuance this overview intentionally summarizes.