What key feature is essential for identifying classified aircraft?

Identifying classified aircraft often relies on examining the fuselage because it contains essential characteristics that differentiate one aircraft from another. The fuselage's shape, size, and design features provide critical information about the aircraft's capabilities and function. These elements are often designed in specific ways to optimize for stealth, aerodynamics, and mission profile, making the fuselage a vital area of focus for identification.

Other features such as weaponry, landing gear, and propellers may also provide insights into the aircraft type and operational role, but they may not carry the same significance as the fuselage in terms of identification. For example, weaponry might change based on the mission or variant, while landing gear configurations can vary widely even among similar aircraft types. Propellers are typically associated with a specific class of aircraft (like propeller-driven planes) but are not as universally applicable for identification as the overall fuselage design. Thus, the fuselage stands out as the key feature for recognizing and determining the classification of various aircraft.