Final answer:
The documents such as crew licenses, Certificate of Airworthiness, and Certificate of Registration are essential for any aircraft to legally operate and comply with aviation regulations.
Step-by-step explanation:
The question pertains to the documents required to be carried onboard an aircraft. These essential documents include the crew licenses, the Certificate of Airworthiness, and the Certificate of Registration. The Certificate of Airworthiness is a document that proves that the aircraft meets all the safety and design requirements set by the aviation authorities. The Certificate of Registration is a document that provides evidence of the aircraft's ownership and nationality. Carrying these documents is crucial for compliance with aviation regulations and for ensuring the aircraft's legality for flight operations.