14 CFR § 121.389 - Flight navigator and specialized navigation equipment.
(a) No certificate holder may operate an airplane outside the 48 contiguous States and the District of Columbia, when its position cannot be reliably fixed for a period of more than 1 hour, without -
(1) A flight crewmember who holds a current flight navigator certificate; or
(b) Notwithstanding paragraph (a) of this section, the Administrator may also require a flight navigator or special navigation equipment, or both, when specialized means of navigation are necessary for 1 hour or less. In making this determination, the Administrator considers -
(1) The speed of the airplane;
(2) Normal weather conditions en route;
(3) Extent of air traffic control;
(4) Traffic congestion;
(5) Area of navigational radio coverage at destination;
(6) Fuel requirements;
(7) Fuel available for return to point of departure or alternates;
(8) Predication of flight upon operation beyond the point of no return; and
(9) Any other factors he determines are relevant in the interest of safety.