What is a major difference between a powerplant inspection and an airframe inspection?

The distinction highlighted in the correct answer revolves around the specific components and systems of an aircraft that each type of inspection targets. Powerplant inspections primarily concentrate on the engine and the associated propulsion systems, which are critical for the aircraft's performance and safety. These inspections ensure that all components of the powerplant, from the engine mechanics to the fuel delivery and ignition systems, are functioning properly and meet regulatory standards.

On the other hand, airframe inspections are geared toward the overall structure and integrity of the aircraft, which includes not only the wings but also the fuselage, landing gear, and control surfaces. This broader focus on the aircraft's structural components ensures that it can withstand various loads, stresses, and environmental factors during operation.

While some other choices mention aspects of inspections, such as the focus areas or frequency of inspections, they do not accurately capture the comprehensive nature of what powerplant and airframe inspections entail in their respective domains. Thus, the emphasis on the distinct areas—engine and propulsion for powerplant and structure for airframe—cements why the selected answer is the most appropriate.