Final answer:
14 CFR Part 91 assigns the responsibility for keeping an aircraft in airworthy condition to the owner or operator. This includes compliance with airworthiness directives, possession of valid documentation, and adherence to approved maintenance programs.
Step-by-step explanation:
14 CFR Part 91 primarily places the responsibility for maintaining an aircraft in an airworthy condition on the owner or operator of the aircraft. This regulation is part of the Federal Aviation Regulations (FARs) that govern all aspects of civil aviation in the United States.
The owner or operator must ensure that the aircraft complies with all the applicable airworthiness directives, has valid documentation, and is maintained according to an approved maintenance program. It is crucial for safety that the aircraft is inspected regularly and kept in a condition for safe operation, as specified by the manufacturer and regulatory authority.