A holder of a pilot license issued in terms of this Part may not exercise the privileges of that license-
(a) unless that person holds an appropriate valid medical certificate issued in terms of Part 67 and complies with all medical endorsements on that medical certificate;
(b) while he or she is aware of having a medical deficiency that would make him or her unable to meet the medical standards for his or her medical certificate, until he or she has been assessed and declared medically fit again by an aviation medical examiner designated in terms of Part 67; or
(c) when he or she is unable to act as a flight crew member of an aircraft because of the circumstances prescribed in Regulations 91.02.3 (1) and (2).