Definitions

This regulation defines key terms used in Part 117, which governs flight and duty time limitations for airline pilots. These definitions matter because they determine how airlines schedule crews and calculate legal duty and rest periods.

Important concepts include:

• Acclimated: You're adjusted to a time zone after 72 hours there or 36 consecutive hours off duty
• Flight duty period (FDP): Starts when you report for a flight assignment and ends when the aircraft is parked with no further movement planned
• Duty: Any task your airline requires, including flights, deadheading, training, and administrative work
• Rest period: Time when you're completely free from all work obligations
• Physiological night's rest: 10 hours of rest including the 0100-0700 window at your home base (or acclimated location)

The regulation also defines reserve types, rest facility classes for augmented operations, and clarifies that deadhead transportation counts as duty, not rest. When definitions conflict with other regulations, Part 117's definitions take precedence for flight and duty time purposes.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*