This paper shows the impact of Federal Aviation Regulations (FAR's) on engine airworthiness. A discussion of FAR's 21 and 33 detailing engine type certification procedures, rules, and policies is provided. This is followed by discussion of the engine/airfrarae interface from an engine certification perspective. Further discussion focuses on the Airworthiness Directive (AD) process, FAR's 11 and 39, as a means of restoring a minimum level of airworthiness for the in-service engine fleet. The concluding remarks reinforce the tenet that FAA's regulations have a positive impact on engine airworthiness.