14 CFR § 117.15 - Flight duty period: Split duty.
For an unaugmented operation only, if a flightcrew member is provided with a rest opportunity (an opportunity to sleep) in a suitable accommodation during his or her flight duty period, the time that the flightcrew member spends in the suitable accommodation is not part of that flightcrew member's flight duty period if all of the following conditions are met:
(a) The rest opportunity is provided between the hours of 22:00 and 05:00 local time.
(e) The rest opportunity is not provided until the first segment of the flight duty period has been completed.
(f) The combined time of the flight duty period and the rest opportunity provided in this section does not exceed 14 hours.