What must be kept on record by an inspection authorization holder for auditing purposes?

The correct answer focuses on the importance of maintaining documentation related to major repairs and alterations performed on aircraft. Inspection authorization holders are required to keep detailed records of significant work completed, as these documents provide a comprehensive history of the aircraft’s maintenance and ensure compliance with regulatory standards set by the FAA.

Maintaining records of major repairs and alterations is crucial for several reasons. It helps ensure the airworthiness of the aircraft, assists in tracking its maintenance history, and can be vital during audits or inspections by regulatory authorities. These records must be precise and readily accessible to demonstrate that the work performed met all applicable airworthiness standards.

Other options mention maintaining records that may have value but do not specifically align with the regulatory requirements for inspection authorization holders. For example, proof of every completed inspection, while useful, is not explicitly mandated for auditing purposes, nor is a simple list of all aircraft worked on. Documentation of all communication with the FAA would not typically fall under the essential records required for demonstrating compliance with major repairs and alterations.