What distinguishes a fixed-wing aircraft from a rotary-wing aircraft?

A fixed-wing aircraft is characterized by its wings, which are rigid and do not move during flight. This design allows these aircraft to generate lift by moving forward through the air, relying on the shape of the wings and the speed of the aircraft.

In contrast, a rotary-wing aircraft, like a helicopter, achieves lift through rotating blades that spin around a vertical axis. These rotating blades cut through the air, creating varying angles of attack and allowing for lift generation in a manner quite different from fixed wings. This fundamental difference in how lift is produced is what primarily distinguishes the two types of aircraft.

The other options relate to characteristics that aren't distinguishing factors between fixed-wing and rotary-wing aircraft. For instance, fixed-wing aircraft can vary greatly in size, and complexities in navigation systems can also vary irrespective of wing type. The focus on the mechanism of lift generation through rotating blades is the essential distinction that defines rotary-wing aircraft.