Which characteristic is essential for materials used in LO aircraft regarding radar?

Nonreflectivity is essential for materials used in low observable (LO) aircraft, as these materials are specifically designed to minimize radar cross-section and reduce the likelihood of detection by radar systems. The fundamental principle behind LO technology is to avoid radar reflection, which can otherwise make an aircraft easily detectable by enemy radar systems.

To achieve this, materials such as radar-absorbent materials (RAM) are used, which are engineered to absorb radar waves instead of reflecting them back. This characteristic significantly contributes to an aircraft's stealth capabilities, allowing it to operate with a higher degree of safety in hostile environments.

While other properties, such as sound insulation or magnetic conductance, may be relevant in broader contexts of aircraft design and function, they do not directly pertain to the primary goal of reducing radar visibility. Therefore, nonreflectivity stands out as the critical characteristic for materials used in low observable aircraft.