Which of the following is NOT a function of fixed-wing capabilities?

Transporting troops directly into combat zones is not typically a function associated with fixed-wing capabilities in a primary context. Fixed-wing aircraft are primarily designed for various roles such as surveillance, air-to-air combat, and logistical support, but direct troop insertion is more heavily associated with rotary-wing aircraft, such as helicopters, which excel in landing and taking off in confined spaces to deploy troops directly into combat zones.

The other options represent functions that fixed-wing aircraft are capable of performing. For instance, air-to-air refueling is a mission that enhances the operational range and endurance of aircraft, enabling them to extend their mission profiles without needing to land. Assisting with field illumination, often achieved through flares or specialized equipment onboard fixed-wing aircraft, is crucial for providing visibility during nighttime operations. Similarly, aviation-delivered ground refueling involves the capability of fixed-wing aircraft to deliver fuel to ground vehicles in deployed settings, further extending the operational reach of ground forces.

Understanding these distinctions helps clarify why direct troop transportation is less aligned with the strengths and primary functions of fixed-wing platforms in modern military operations.