[apcherry]

A common fallacy I'm afraid - modern fighter planes are unstable for improved supersonic performance - reduced drag. So relaxed stability may benefit civil aircraft in terms of fuel efficiency. There is an argument that inherently unstable aircraft makes the manoeuvrability worse or harder. What many forget is that issue with manoeuvrability is actually at the end of the manoeuvre. The handling qualities aim is to point the nose in a new direction and an unstable aircraft makes the design challenge harder to stop the aircraft at the position required.