Which of the following could be a consequence of neglecting low observable maintenance on aircraft?

Neglecting low observable maintenance on aircraft can lead to increased radar detection. Low observable technology is specifically designed to minimize an aircraft's radar signature, which allows it to evade enemy detection systems. If maintenance on these systems is not performed, it can result in deterioration of the materials and coatings that contribute to the aircraft’s stealth capabilities. This deterioration increases the aircraft’s radar cross-section, making it more detectable by enemy radar systems, thus compromising its effectiveness in combat scenarios where stealth is a critical factor.

The other answer choices suggest positive outcomes, which are unlikely to occur from neglecting low observable maintenance. For instance, improved fuel efficiency is generally associated with well-maintained systems that optimize performance, not with neglect. Similarly, longer lifespan and enhanced combat capabilities typically result from regular maintenance and care, rather than neglect, which could ultimately decrease an aircraft's operational effectiveness and longevity.