What is FAR Part 117?
14 CFR Part 117 — Flight and Duty Limitations and Rest Requirements: Flightcrew Members — is the FAA's fatigue regulation for scheduled domestic, supplemental, and flag operations under Part 121. It replaced the old Part 121.470/.480/.481 rules in 2014 and brought significant changes: hard flight-time caps in rolling windows, a science-based duty-period table (FDP Table B), and explicit rest minimums between duty periods.
Part 117 does not apply to Part 91, Part 135 charter (which has its own less-strict 117-equivalent under Subpart F), or Part 142 training centers. Operators frequently apply Part 117-equivalent enforcement voluntarily because it's the easiest framework to design around.
The four rolling-window caps
Part 117 caps flight time — that's actual flying, not duty time — in four rolling windows. The lookback is continuous: at any moment, the most recent 24 hours, 168 hours (7 days), 672 hours (28 days), and 8,760 hours (365 days) must not exceed their caps.
- •117.13: 8 hours flight time in any 24-hour period (unaugmented operations)
- •117.23(a)(1): 30 hours flight time in any 168 hours (7-day rolling window)
- •117.23(a)(2): 100 hours flight time in any 672 hours (28-day rolling window)
- •117.23(a)(3): 1,000 hours flight time per calendar year (rolling 12 months in practice)
Flight Duty Period (FDP) — Tables B and C
Flight Time isn't the only cap. Flight Duty Period — the time from report to release — is also limited, and it varies based on report time of day and number of flight segments. FAR 117 Table B is the unaugmented FDP table: an early-morning report (0500-0559 local) for 4+ flight segments caps FDP at 11 hours. A late-morning report (0700-1259) for 1-2 segments allows up to 13 hours.
Augmented crew operations (3 or 4 pilots) operate under Table C, with extensions for inflight rest facilities. A long-haul augmented-crew FDP can stretch to 17+ hours when Class 1 rest facilities are present.
Rest requirements between duty periods
117.25 governs the rest you owe a crew member between duty periods. The baseline: 10 hours of rest immediately preceding the FDP, with 8 of those hours sleep opportunity. Operators can't compress rest below 10 hours; if a previous duty pushes the rest window late, the subsequent FDP is delayed.
Cumulative rest is also tracked: 117.25(d) requires 30 consecutive hours free of duty in every 168-hour window. This means a pilot can't string seven consecutive 14-hour duty days even if each day's rest meets the 10-hour minimum.
What software enforcement actually looks like
A pilot scheduling system that 'supports FAR 117' should mean two things. First: at the moment of booking, the system computes the proposed flight's contribution to each of the four rolling windows for the assigned pilot and rejects the booking if any cap busts. Second: the system surfaces the pilot's current window utilization (24h / 168h / 672h) on the duty board so dispatchers and chief pilots can see exhaustion approaching before they create a new conflict.
Reports-based enforcement — running a weekly query for over-cap pilots — is too late. Real enforcement happens at the mutation layer, server-side, with a hard transaction reject. AviationAlley's checkFar117 function (packages/api/src/lib/far117.ts) is built this way; the booking mutation throws FORBIDDEN with a violation message naming the specific window.
Exceptions, extensions, and operator-specific rules
117.19 governs FDP extensions for unforeseen circumstances — typically weather, ATC, or mechanical delays. Captains can extend FDP up to 2 hours beyond the table at their discretion, with reporting required. Operator-specific Operations Specifications (OpSpecs) can also override Part 117 defaults in specific cases (split duty rest, equivalent-rest workarounds for time-zone changes).
Long-haul operators with augmented crew rules and inflight rest facilities operate under a more permissive set of constraints. A 4-pilot crew with Class 1 rest facilities can sustain FDPs of 17+ hours under Table C; the same crew with Class 3 rest facilities (no separated bunk) might cap at 14 hours.
Frequently asked questions
Does FAR 117 apply to Part 135 charter operators?
No — Part 135 has its own rest and duty rules under Subpart F (135.261 to 135.273). They're generally less restrictive than Part 117. Some Part 135 operators choose to apply Part 117 voluntarily because it's the easiest framework to design tools around.
What's the difference between flight time and duty time under Part 117?
Flight time is wheels-up to wheels-down — what actually counts toward the rolling-window caps. Duty time is the broader period from report-for-duty to release. FDP (Flight Duty Period) is the duty time that includes flight segments. A pilot can have a 13-hour FDP with only 6 hours of flight time inside it.
Can a pilot waive Part 117 caps?
No. The caps are hard regulatory limits, not contractual ones. A pilot who agrees to fly over-cap and a dispatcher who assigns them both violate Part 117. Operator-level OpSpecs can adjust specific rules (rest definitions, augmented-crew thresholds) with FAA approval, but the rolling-window flight-time caps are not waivable.
How do operators handle Part 117 across time zones?
Part 117 caps flight time, which is calendar-neutral — the rolling windows are wall-clock based on the pilot's report-time zone. Operations Specifications (OpSpecs) typically govern time-zone-acclimation rules (when a pilot is 'acclimated' to a new zone affects FDP table choice). Most operators define acclimation as 72 consecutive hours in a zone.
Related guides
How to set up a 14 CFR Part 142 training center
Part 142 is the FAA certificate for sim-based training centers — separate from Part 141 schools and Part 121 airlines. This is the practical guide to setting one up, from the FSDO meeting to the first NSP evaluation.
AAIP for Part 135 operators: a complete compliance guide
The Approved Aircraft Inspection Program (AAIP) is the maintenance backbone of a Part 135 charter operation. This guide walks through what AAIP requires, how to maintain compliance, and how to prove it during PMI surveillance.
Airworthiness Directives (ADs) — a practical compliance guide
ADs are mandatory FAA actions you must take on specific aircraft, engines, propellers, or appliances. This is the practical guide to tracking them, complying on time, and proving it during inspection.