14 CFR § 121.493
Flight time limitations: Flight engineers and flight navigators
July 13, 2020
(a) In any operation in which one flight engineer or flight navigator is required, the flight time limitations in §121.483 apply to that flight engineer or flight navigator.
(b) In any operation in which more than one flight engineer or flight navigator is required, the flight time limitations in §121.485 apply to those flight engineers or flight navigators.