What must be done if a dangerous good, such as a weapon, is discovered in an inaccessible baggage compartment during a flight?

When a dangerous good, such as a weapon, is discovered in an inaccessible baggage compartment during flight, the appropriate response is to divert the flight immediately. This action is taken to ensure the safety of everyone on board and to prevent any potential threat the item may pose.

Diverting the flight allows for the cargo to be addressed in a secure manner, ensuring that appropriate authorities can handle the situation safely once the aircraft lands. Keeping the aircraft on its current course could pose risks not only to the passengers and crew but potentially to air traffic and local jurisdictions upon arrival.

The other responses do not adequately address the safety concerns involved. Ignoring the discovery poses a substantial risk, and although notifying authorities after landing is important, it does not address the immediate threat during the flight. Securing the area and continuing to the destination also fails to prioritize the safety necessary in such scenarios. Therefore, diverting the flight is the only course of action that adequately mitigates the risks associated with the presence of dangerous goods.