Which safety measure should be implemented prior to jacking an aircraft?

The correct safety measure to implement prior to jacking an aircraft is to install critical stress panels or plates. This practice is essential because it helps to distribute the load evenly across the aircraft's structure during the jacking process. Aircraft are designed with specific structural points that can bear loads, and jacking can potentially create stress concentrations in areas that might not be reinforced for such forces. By using stress panels or plates, you reduce the risk of damaging the aircraft’s structure and ensure that it remains stable while elevated.

While other options might seem relevant to aircraft safety, they do not directly address the specific needs and precautions necessary when preparing to jack an aircraft. For instance, removing access panels is not a standard requirement and could leave essential components exposed rather than facilitating the jacking process. Ensuring fuel tanks are full is generally not advisable, as jacking should occur with minimal weight from fluids to maintain stability. Disconnecting the battery is a standard safety practice to prevent electrical hazards but is not directly tied to the jacking process itself. Therefore, the installation of critical stress panels is the most pertinent action to take prior to jacking an aircraft to ensure safety and structural integrity.