Answer :
The statement about the flight deck door remaining locked for the entire duration of a flight is generally false, as there can be exceptions based on specific airline regulations and situations. The statement is false.
The statement about the flight deck door being locked from the time the airplane initiates a flight segment until the end of that flight segment deals with aviation safety protocols. The assumption behind this statement seems to reflect post-9/11 security measures where cockpit access is highly restricted to ensure the safety of the flight crew and passengers. However, as policies may vary by airline and over time, this statement cannot be universally declared as true without specific context to airline regulations and emergency protocols. Therefore, in a general sense, this statement is false as there are cases, such as when a pilot needs to use the restroom or during crew changes on long-haul flights, where the door may be opened.
