(a) During takeoff and landing, and while en route, each required
flight crewmember shall --
(1) Be at the crewmember station unless the absence is necessary to
perform duties in connection with the operation of the aircraft or in
connection with physiological needs; and
(2) Keep the safety belt fastened while at the crewmember station.
(b) Each required flight crewmember of a U.S.-registered civil aircraft
shall, during takeoff and landing, keep his or her shoulder harness
fastened while at his or her assigned duty station. This paragraph does
not apply if --
(1) The seat at the crewmember's station is not equipped with a
shoulder harness; or
(2) The crewmember would be unable to perform required duties with the
shoulder harness fastened.