According to JAR-145, what must be issued after a kind of maintenance?

The correct answer is the Certificate of Release to Service. This document is crucial in the context of aircraft maintenance and is issued to confirm that the work has been carried out in accordance with applicable air safety regulations, ensuring that the aircraft is safe to return to operation.

The Certificate of Release to Service acts as an official record that the required maintenance, inspections, or repairs have been completed and that they meet the necessary standards mandated by regulatory authorities such as the JAA (Joint Aviation Authorities) or the FAA (Federal Aviation Administration). This certification is vital for maintaining compliance and ensuring the safety of aviation operations.

Other options might seem relevant but do not serve the same purpose. A maintenance statement, for instance, may provide details about what was done, but it lacks the official recognition and regulatory compliance necessary for safety assurance. The Certificate of Airworthiness, while important, is a document that certifies an aircraft's overall fitness for flying, typically issued after extensive evaluations, rather than immediately following maintenance. A Certificate of Completed Service might imply that service was performed, but it is not the formal document specified by regulations like JAR-145 that ensures the aircraft is ready for return to service after maintenance.