What must not occur for a person to act as a required flight crew member?

To act as a required flight crew member, it is essential that individuals be aware of their medical fitness to fly because any medical condition that affects safety can significantly jeopardize not only their own safety but also the safety of others on board and on the ground. If a person unknowingly has a medical condition that could impair their ability to perform safely, they may not be in a position to fulfill their responsibilities effectively. Without knowledge of the medical condition, they cannot take the necessary precautions or seek proper treatment, thereby potentially creating a hazardous situation during flight operations.

Having a flight instructor endorsement, current flight experience, and having completed a preceding flight review are all important requirements for flight crew members. These ensure that the crew is qualified, has the requisite flying skills, and is up-to-date on regulations and operations. However, if a crew member is unaware of a medical condition affecting their ability to operate safely, that presents a more critical risk that ultimately prevents them from fulfilling their role effectively.