Which entity is ultimately responsible for keeping the aircraft airworthy?

The owner of the aircraft holds the ultimate responsibility for ensuring that the aircraft remains airworthy. This includes maintaining compliance with all regulatory requirements, proper maintenance schedules, and ensuring that the aircraft is operated in accordance with airworthiness directives.

While the maintenance organization performs necessary inspections and repairs, and the pilot operates the aircraft and ensures it is fit for flight before each journey, the ultimate responsibility lies with the owner. This responsibility can encompass several factors, including financial investment in proper maintenance, ensuring all appropriate records are kept, and fulfilling legal obligations set forth by aviation authorities.

The roles of the engineer and the maintenance organization are vital for performing technical work and ensuring the aircraft's components are functioning correctly. However, these functions are not solely responsible for the overall airworthiness status. The pilot plays a crucial role in assessing the aircraft's condition just before flight, but it is the owner who has the overarching duty to manage and maintain the aircraft's airworthiness throughout its operational lifecycle.