What happens to air as it is compressed and then allowed to expand around the aircraft?

When air is compressed and then allowed to expand around an aircraft, it creates drag. This phenomenon is primarily due to the fact that as air moves over the aircraft surface, it experiences changes in pressure and velocity.

During the compression phase, air molecules are forced closer together, which can lead to increased pressure. As the compressed air then expands, it accelerates over the surface of the aircraft. The interaction of the fast-moving air with the aircraft generates a form of resistance that is categorized as drag.

This drag arises from two main sources: skin friction drag, which is the result of viscosity and the interaction of the air with the aircraft surface, and pressure drag, related to the differences in pressure created by the airflow around the aircraft shape. The shape and design of the aircraft aim to minimize this drag for efficient flight.

The other options do not apply in this scenario. Speed loss would refer to a reduction in velocity, which does not specifically result from the process of air compression and expansion. While expanded air can contribute to thrust in specific contexts (like in jet engines), the overall effect on aircraft flight, particularly concerning airflow around the wing and body, is the creation of drag. Lift is influenced by airflow over the wings but is not a direct