Crew Duty Time

Crew duty time is the total period during which a flight crew member is considered to be on duty, beginning from the time they are required to report for a flight assignment and ending when they are released from all responsibilities following the final flight of the assignment. Aviation regulations prescribe maximum duty time limits and minimum rest intervals to manage the fatigue risk that is inherent in irregular schedules, night operations, and time zone crossings.

What Is Crew Duty Time?

FAA Part 117, which governs duty time for U.S. airline pilots under 14 CFR, defines a "flight duty period" (FDP) as the time from when a crew member reports for a flight assignment until the aircraft is parked and engines are shut down at the conclusion of the final flight. The maximum FDP varies based on the number of flight segments, the time of day (with the most restrictive limits applying to periods that include the window of circadian low between 0200 and 0559 local time), and whether a rest facility is available aboard the aircraft for augmented crew rest. For a standard two-pilot operation starting at 0600, the maximum FDP is typically 9 hours with up to 4 flight segments. Adding a third or fourth pilot and providing onboard rest extends the permitted FDP to 13 or 17 hours depending on the quality of the rest facility.

How It Works in Practice

A typical crew duty day begins with a report time 60 minutes before departure for domestic flights and 90 minutes for international flights. The crew completes pre-flight planning, weather briefings, aircraft walk-arounds, and ATC coordination before the first engine start. Each subsequent sector within the FDP adds to the cumulative block time toward the pilot's daily flight time limit (8 or 9 hours depending on segment count) while the FDP clock runs continuously. Upon completing the final sector, the crew reports "in" and the FDP officially ends. They must then receive a minimum rest period of 10 consecutive hours (or more, depending on the length of the preceding FDP) before the next FDP can begin.

Airlines use crew scheduling software — systems like AIMS, Sabre CrewTracker, or Jeppesen PBS — to build crew pairings that comply with FAT (Flight and Duty Time) regulations across every leg while optimizing cost and crew quality of life. When irregular operations compress planned rest windows below minimums, the crew legally cannot operate the next flight until the rest minimum is satisfied, which can cause cascading cancellations or necessitate deadheads of replacement crews.

Why It Matters

Fatigue is one of the most thoroughly documented contributors to aviation accidents. The 2009 Colgan Air crash near Buffalo, New York — which killed 50 people and was attributed in part to crew fatigue — directly triggered the U.S. Congress to mandate Part 117's revisions, which took effect in 2014. The revised rules imposed significantly stricter rest requirements, particularly for operations that cross the circadian nadir, and established science-based duty time limits aligned with ICAO standards. EASA's EU-OPS Flight and Duty Time regulations similarly restrict European airline operations, and ICAO Annex 6 sets global minimum standards that national regulations must meet or exceed.

For airlines, crew duty time limits are a core capacity constraint in schedule building. A flight that arrives late, pushing a crew beyond their FDP limit, legally cannot depart with that crew, regardless of commercial pressure. The resulting need for "hot spares" — reserve crews positioned at key hubs to replace duty-limited crews — is a significant operational planning and cost challenge.

Key Facts and Figures

• FAA Part 117 maximum single-day FDP for a two-pilot crew starting between 0500 and 0559: 9 hours.
• Maximum daily flight time (block hours) for a Part 117 airline pilot: 8 hours for schedules with 3 or fewer segments, 9 hours for schedules with up to 4 segments.
• Augmented crew rest in a seat reduces the FDP extension to 13 hours; a lie-flat bunk rest facility allows up to 17 hours.
• The 2014 Part 117 implementation was the most significant revision to U.S. crew rest rules since 1985 and was directly linked to the Colgan Air 3407 accident investigation.
• EASA regulations require a minimum 11-hour rest between duty periods for European airline crews, compared to the FAA's 10-hour minimum.
• Cumulative fatigue limits: FAA caps airline pilots at 100 flight hours per rolling 28 days, 1,000 hours per calendar year, and 100 hours per rolling 28-day period.

Related Concepts

Flight Time Limitations, WOCL, Augmented Crew, Part 117, Fatigue Risk Management