What characteristic must each aircraft used for flight instruction possess?

Each aircraft used for flight instruction must be properly registered with the relevant aviation authority, which in this case is the Michigan Aeronautics Commission. This registration is essential for ensuring that the aircraft meets all safety and regulatory standards necessary for flight operations. Proper registration signifies that the aircraft has passed inspections and is compliant with maintenance requirements, making it suitable for instructional purposes. Regulatory compliance helps protect both the instructors and students by ensuring that the aircraft has met the necessary legal and safety standards to operate in the airspace.

While other options may seem relevant, they do not align with the fundamental regulatory requirements for flight instruction. For instance, custom paint jobs, while possibly enhancing visibility or recognition, do not impact the aircraft's operational safety. Long-distance flight capabilities are not a requisite for instructional aircraft, as the training often involves local flights and short-duration missions. Additionally, regarding ownership, the instructional aircraft do not necessarily need to belong to the instructor; rather, they must be properly registered to ensure legitimacy and safety in training operations.