Which document is essential for executing a solo flight?

For a solo flight, a pilot must have a specific make and model endorsement in their logbook from their flight instructor. This endorsement confirms that the pilot has been sufficiently trained and is competent to operate that particular aircraft solo. The endorsement is a legal requirement and serves as a safeguard to ensure that the pilot is familiar with the aircraft's systems, controls, and operating procedures.

While the other documents mentioned are important for different aspects of aviation, they do not specifically pertain to the authorization required for solo flight. The aircraft registration document establishes ownership and airworthiness of the aircraft, but it does not grant pilot proficiency. A maintenance report indicates that the aircraft is in a safe operating condition but does not address the pilot's qualifications. The pilot medical certificate is necessary to ensure that the pilot is physically fit to fly, yet it alone does not indicate the specific training needed to operate a particular aircraft solo. Therefore, the endorsement is the critical document needed for this scenario.