Final answer:
An amateur built aircraft is required to have an 'Experimental - Amateur-Built' airworthiness certificate from aviation authorities, ensuring it meets safety standards. Advance from balsa wood to plastics has improved model airplane durability.
Step-by-step explanation:
An amateur built aircraft typically uses a special airworthiness document issued by aviation authorities. This document is known as an "Experimental - Amateur-Built" airworthiness certificate. Such documents are required to ensure that the aircraft meets a certain level of safety and is suitable for operation. While the construction of model airplanes has evolved from materials like balsa wood to more durable plastics, the principles of airworthiness apply to full-scale amateur-built aircraft, requiring adherence to safety standards and regulations set forth by aerospace organizations such as the American Institute of Aeronautics and Astronautics (AIAA).