FTDT Calculator — USA (FAR Part 117)

Updated: 2026-08-08 07:02 ET · Audited: 2026-06-26

The Calculator determines Flight Duty Period legality based on flight operation characteristics and flight crew status. It also determines cumulative FDP hours, cumulative Flight Time hours, and remaining hours against each Part 117 limitation.

Engine status: The 1908 rules engine ships behind GatedFTDTCalculationEngine — Release builds default to the legacy engine, DEBUG builds default to shadow mode (both engines run, legacy result surfaces; see ALPAMobile/Helpers/AppPropertiesFeatureFlags.cs). The §117.25(d) timezone-dependent logic is implemented but dormant until the backend airports API ships timezone fields (ALPAMobile/Services/DataManagerAirportLookup.cs; backend ask tracked as ALPA Services AB#2371).

Flight Time Limit (FTL)

Unaugmented — Table A

For unaugmented operations the maximum FTL is determined by the acclimated time of report per Table A to Part 117.

Time of Report (Acclimated)	Maximum Flight Time (hours)
0000–0459	8
0500–1959	9
2000–2359	8

Augmented — Table C

For augmented operations the maximum FTL is determined by Table C to Part 117, based on scheduled start time, total crew count (3 or 4 pilots), and rest facility class (1, 2, or 3). Limits range from 13 to 19 hours.

Maximum Flight Duty Period (FDP)

The Maximum FDP is reduced by 30 minutes if the flight crew member is not acclimated.

Unaugmented — Table B

Note: Deadhead transportation is duty but is NOT counted as a flight segment for Table B purposes (§117.3). If a deadhead segment causes the FDP to exceed the Table B limit, see §117.25(g) rest requirements.

Scheduled Start Time (Acclimated)	1 seg	2 seg	3 seg	4 seg	5 seg	6 seg	7+ seg
0000–0359	9	9	9	9	9	9	9
0400–0459	10	10	10	10	9	9	9
0500–0559	12	12	12	12	11.5	11	10.5
0600–0659	13	13	12	12	11.5	11	10.5
0700–1159	14	14	13	13	12.5	12	11.5
1200–1259	13	13	13	13	12.5	12	11.5
1300–1659	12	12	12	12	11.5	11	10.5
1700–2159	12	12	11	11	10	9	9
2200–2259	11	11	10	10	9	9	9
2300–2359	10	10	10	9	9	9	9

All values in hours.

Augmented — Table C

For augmented operations, FDP is determined by three factors: (1) acclimated scheduled start time, (2) total crew count (3 or 4 pilots), and (3) rest facility class (1, 2, or 3).

Important: The maximum augmented FDP is not a flat value per crew count. It depends on all three factors. Minimum possible: 13 hours (Class 3 / 3 pilots / 0000–0559). Maximum possible: 19 hours (Class 1 / 4 pilots / 0700–1259).

Start Time (Acclimated)	Class 1 / 3 crew	Class 1 / 4 crew	Class 2 / 3 crew	Class 2 / 4 crew	Class 3 / 3 crew	Class 3 / 4 crew
0000–0559	15	17	14	15.5	13	13.5
0600–0659	16	18.5	15	16.5	14	14.5
0700–1259	17	19	16.5	18	15	15.5
1300–1659	16	18.5	15	16.5	14	14.5
1700–2359	15	17	14	15.5	13	13.5

All values in hours. Rest facility class definitions: see definitions.html.

Reserve (RAP) Calculations

Unaugmented: Total hours in FDP + RAP may not exceed the lesser of: (Table B FDP) + 4 hours, or 16 hours — measured from the beginning of the RAP.

Augmented: Total hours in FDP + RAP = (Table C FDP) + 4 hours — measured from the beginning of the RAP. No 16-hour absolute cap for augmented.

FDP End Time

To determine when the FDP reaches its maximum: add the maximum FDP (from Table B or C) to the FDP start time.

Actual Flight Time

The actual flight time equals the sum of durations of all city-pair segments flown.

Cumulative Limitations

Window	Type	Maximum
Last 672 hours (28 days)	Cumulative Flight Time (§117.23(b))	100 hours
Last 365 days	Cumulative Flight Time (§117.23(b))	1,000 hours
Last 168 hours (7 days)	Cumulative FDP hours (§117.23(c))	60 hours
Last 672 hours (28 days)	Cumulative FDP hours (§117.23(c))	190 hours

Rest Period Requirements (§117.25)

§117.25(a) — No Assignment During Required Rest

No certificate holder may assign and no flightcrew member may accept assignment to any reserve or duty during any required rest period.

§117.25(b) — Weekly Rest (168-Hour Window)

Before beginning any reserve or flight duty period, a flightcrew member must be given at least 30 consecutive hours free from all duty within the past 168 consecutive hour period.

Code requirement: Check that FDP start time is preceded by at least 30 consecutive duty-free hours within the prior 168-hour window.

§117.25(c) — New Theater Acclimation Credit

If a flightcrew member operating in a new theater has received 36 consecutive hours of rest, that flightcrew member is considered acclimated and the rest meets the requirements of §117.25(b).

§117.25(d) — Trans-Theater Home Base Rest

A flightcrew member must receive a minimum of 56 consecutive hours rest upon return to home base if:

Travels more than 60° longitude during an FDP or series of FDPs, AND
Is away from home base for more than 168 consecutive hours.

The 56 hours must encompass three physiological nights' rest based on local time.

Code requirement: Track home base departures and trans-theater travel distance; flag when 56-hour rest with 3 physiological nights is required.

§117.25(e) — Pre-FDP Rest (10 Hours / 8-Hour Sleep Opportunity)

A flightcrew member must be given a rest period of at least 10 consecutive hours immediately before beginning the reserve or flight duty period (measured from release from duty). The 10-hour rest period must provide at least 8 uninterrupted hours of sleep opportunity.

Code requirement: Pre-FDP rest gap must be ≥10 hours from end of prior duty. Display the available sleep opportunity within that window.

§117.25(f) — Flightcrew Member Notification Obligation

If a flightcrew member determines that the rest period under §117.25(e) will not provide 8 uninterrupted hours of sleep opportunity, the flightcrew member must notify the certificate holder and cannot report for the assigned FDP until a proper rest period is received.

Code requirement (informational): App should note when the rest window provides fewer than 8 hours of sleep opportunity.

§117.25(g) — Deadhead Transportation Overage

If a flightcrew member engaged in deadhead transportation exceeds the applicable Table B FDP, the flightcrew member must be given a rest period equal to the length of the deadhead transportation (but not less than the 10-hour minimum under §117.25(e)) before beginning a flight duty period.

Code requirement: When a deadhead segment causes total FDP to exceed the Table B limit, calculate and display required post-deadhead rest: max(deadhead duration, 10 hrs).

Notes

For Split Duty operations, the Rest Opportunity (RO) does not count as FDP hours.
For Reserve Operations, RAP time does count as FDP hours.
Split Duty Rest Opportunity (RO): must occur between 22:00 and 05:00 and have a minimum duration of 3 hours (§117.15).
The Maximum FDP is reduced by 30 minutes if the flight crew member is not acclimated.
Airport standby and Long-Call reserve use non-reserve operation types (see duty-period-us.html).