In the context of aviation regulations, which document certifies the airworthiness of an aircraft?

The Airworthiness Certificate is the correct document that certifies the airworthiness of an aircraft. This certificate indicates that the aircraft meets the safety and performance standards set by aviation regulatory authorities. It ensures that the aircraft has been inspected and found to be in compliance with all applicable standards and regulations, confirming it is safe to fly.

An Operator Certificate pertains to the approval for a company to conduct commercial flight operations, but it does not specifically certify the airworthiness of an individual aircraft. A Pilot Certificate verifies that an individual has received the necessary training and is qualified to operate an aircraft, but again, it does not deal with the aircraft's airworthiness. Similarly, a Flight Certificate is not a commonly recognized term in aviation regulations and does not refer to a specific certification regarding aircraft airworthiness.