67.—(1) An aircraft registered in the United Kingdom must carry a flight crew adequate in number and description to ensure the safety of the aircraft.
(2) An aircraft—
(a)which has a flight manual, must carry a flight crew of at least the number and description specified in that flight manual;
(b)which does not currently have a flight manual but has done in the past, must carry a flight crew of at least the number and description specified in that flight manual.