Which term describes the way an aircraft reacts to disturbances in flight?

The term that best captures how an aircraft reacts to disturbances during flight is quasi-static stability. This concept refers to the ability of an aircraft to return to a state of equilibrium after experiencing disturbances, be they small or large. Quasi-static stability takes into account the aircraft's design and aerodynamic characteristics, determining how it will behave in response to factors such as turbulence or control inputs.

Understanding this stability is crucial for pilots, as it affects how they manage the aircraft during various phases of flight. An aircraft with good quasi-static stability will have a natural tendency to return to its original flight path after being disturbed, thereby providing a more manageable and predictable flight experience.

The other options refer to different aspects of aircraft performance. Static equilibrium refers to a condition where all forces acting on the aircraft are balanced, but it does not specifically address the dynamic reactions to disturbances. Dynamic performance pertains to how the aircraft performs under various flight conditions, focusing more on efficiency and responses based on control inputs rather than stability. Flight responsiveness relates to how quickly and effectively an aircraft can respond to pilot inputs, which is an important aspect of control but does not encompass the broader concept of stability in response to external disturbances.