The Rule Is a Ceiling, Not a Target

Part 117 sets maximum flight time, duty time, and minimum rest requirements based on when a pilot’s trip starts, how many time zones it crosses, and how many legs are flown. It is often described as a formula: plug in the report time and get a duty limit. That description is not wrong, but it is incomplete. The regulation exists because fatigue degrades judgment, reaction time, and situational awareness in ways a pilot often cannot self-assess in the moment. Meeting the numeric limits is the floor. It is not evidence that a specific pilot, on a specific trip, was fit for duty.

Where Fatigue Risk Management Actually Lives

A Fatigue Risk Management Plan, required of every Part 121 carrier under Section 121.473, is supposed to be where the gap between legal and fit for duty gets addressed: education, reporting, and a real feedback loop between crews and scheduling. In practice, I see FRMPs that exist as a compliance document and nothing else, with no fatigue reporting culture, no scheduling response to fatigue calls, and no data feeding back into how trips get built. Part 135 operators have even less structure, since Sections 135.263 through 135.273 place more of the burden on the operator’s own policies and culture, with less regulatory scaffolding underneath.

What This Looks Like in a Case

When fatigue becomes a factor in litigation or an incident investigation, the numeric duty limits are rarely where the real analysis happens. The questions that matter are whether the operator had a functioning fatigue reporting system, whether crew concerns were acted on, and whether the trip in question was built in a way that a reasonable scheduling department should have flagged. An operator that can show a live, used FRMP is in a very different position than one that can only show a document that has never been tested.

Part 117 compliance is necessary. It is not the same thing as a fatigue management program, and the distinction is exactly where I spend most of my time in this practice area.