Which part governs the issuance of an Airworthiness Certificate?

The issuance of an Airworthiness Certificate is governed by 14 CFR Part 21, which outlines the requirements for the certification of aircraft and the procedures for obtaining an Airworthiness Certificate. This part establishes the rules for when an aircraft can be considered safe for flight and defines the necessary qualifications that must be met before an airworthiness certificate can be issued. It encompasses not just the criteria for aircraft design and manufacturing but also for modifying existing aircraft and ensuring compliance with safety standards.

In contrast, while 14 CFR Part 39 deals with the airworthiness directives and mandatory actions for maintaining safety, and 14 CFR Parts 23 and 25 outline the airworthiness standards for small and large airplanes respectively, these parts do not directly govern the process of issuing the Airworthiness Certificate itself. Instead, they establish criteria related to aircraft performance and safety that must be satisfied to attain the certification status outlined in Part 21. Thus, Part 21 is the key regulation for the issuance of Airworthiness Certificates.