(b) A required flight crewmember may leave the assigned duty station—
(1) If the crewmember's absence is necessary for the performance of duties in connection with the operation of the airplane;
(2) If the crewmember's absence is in connection with physiological needs; or
(3) If the crewmember is taking a rest period and relief is provided—
(i) In the case of the assigned pilot in command, by a pilot qualified to act as pilot in command.
(ii) In the case of the assigned second in command, by a pilot qualified to act as second in command of that airplane during en route operations. However, the relief pilot need not meet the recent experience requirements of §125.285.