Who is primarily responsible for ensuring an aircraft is maintained in an airworthy condition?

The primary responsibility for ensuring an aircraft is maintained in an airworthy condition lies with the owner or operator. This responsibility is established under aviation regulations, which assign the owner/operator the obligation to ensure that all maintenance, preventive maintenance, and alterations are performed in accordance with the applicable regulations and standards. The owner/operator must also ensure that the aircraft is operated in compliance with the conditions of its airworthiness certificate.

While the pilot in command certainly plays a significant role in pre-flight inspections and ensuring the aircraft is safe before each flight, their responsibilities are more focused on the immediate operation of the aircraft rather than its overall maintenance. Meanwhile, the maintenance crew plays a critical role in performing the actual maintenance tasks, but they work under the authority and obligations set forth by the owner/operator. Flight instructors, while knowledgeable and responsible for training pilots, do not have the direct responsibilities concerning the airworthiness of the aircraft as they do not own or operate it in the same sense.

Thus, the owner or operator is ultimately accountable for the overall airworthiness and ongoing maintenance of the aircraft, making this option the correct choice.