What is defined as an unauthorized person on an aircraft not listed on the flight manifest?

The term that refers to an unauthorized person on an aircraft who is not listed on the flight manifest is a stowaway. A stowaway typically boards an aircraft without permission, often hiding in areas where they cannot be easily seen or accessed, such as cargo holds or hidden compartments. This poses significant security risks, as well as safety issues, because these individuals have not gone through the necessary security screenings or procedures designed to ensure passenger safety.

The other terms provided do not accurately describe the situation. Loiterers generally refer to individuals lingering in an area without a purpose but do not inherently imply unauthorized access to an aircraft. Hitchhikers, similarly, are those seeking a ride, typically on land, and do not relate to the air travel context. Tourists are legitimate passengers who follow all the necessary protocols to board, making them completely different from a stowaway. Recognizing the distinction between these terms helps reinforce the importance of security measures in air transportation.