Final answer:
An aircraft is most stable longitudinally when its center of gravity is well forward of the center of pressure, creating a self-righting effect.
Step-by-step explanation:
An aircraft has greater longitudinal stability when the center of gravity is well forward of the center of pressure. This arrangement provides stability because it aligns the aircraft's natural tendency to right itself in the event of a disturbance, much like a dart that remains point-forward during flight due to its weight distribution. A forward center of gravity relative to the center of pressure ensures that any increase in the angle of attack generates a restoring moment that pushes the nose back down, while a rearward shift in the center of gravity could cause the nose to pitch up further, leading to potential instability or even a stall.