What does the FOM state about the use of oxygen masks during flight?

The FOM clearly states that pilots are required to don oxygen masks if there is a loss of cabin pressure, as this is a critical safety procedure during such emergency situations. The use of oxygen masks is designed to ensure that pilots maintain their ability to operate the aircraft safely under conditions where normal cabin pressure cannot be maintained. Following the emergency protocols after donning the masks is essential, as it ensures that all necessary actions are taken to manage the situation effectively, maintain control of the aircraft, and prioritize the safety of both crew and passengers. This requirement is rooted in the need for immediate and appropriate responses in sudden decompression events, highlighting the importance of preparation and understanding procedures among flight crews.

The other options do not capture the mandatory aspect of the protocols for pilots or misinterpret the requirements for passengers. Use at pilot discretion and oxygen being optional undermines the safety regulations that govern flight operations in regards to cabin pressure loss.