What is not a factor of in-flight stability?

In-flight stability primarily depends on factors that ensure an aircraft maintains its intended flight path and responds predictably to control inputs. Proper alignment is not a direct factor of in-flight stability in the same way that the other options are.

Proper weight influences how an aircraft behaves in the air, including its ability to maintain altitude and maneuver. An appropriate drag surface impacts how the aircraft interacts with airflow, which is crucial for maintaining stability during flight. Proper air speed is vital for ensuring that the aerodynamic forces acting on the aircraft promote stability.

While alignment can be significant for initial flight setup, it does not directly govern stability during flight once the aircraft is airborne.