Final answer:
Responsibility for an adult passenger not wearing a seatbelt typically falls on the passenger, but local or state laws may also hold the driver accountable.
Step-by-step explanation:
In the case where a passenger in the front seat over 18 years old is caught not wearing a seatbelt, the responsibility largely falls on the passenger themselves. This is because individuals over the age of 18 are generally considered legally responsible for their own actions, including compliance with safety laws such as seatbelt use. However, there could be exceptions depending on specific local or state laws where the driver could also be held responsible for ensuring that all passengers are wearing seatbelts.
It's worth noting that while the question appears to be asking about a traffic law scenario, the case study provided, 'FLIGHT RISK', relates to aircraft travel and not automotive travel. Here, the example describes a situation in which passengers on a plane are allowed to unbuckle their seatbelts when the pilot indicates it is safe to do so. This serves as an illustration of how different modes of transportation can have different safety regulations.