Static stability deals with the initial response to a perturbation whilst dynamic stability deals with the behaviour thereafter.

A fly-by-wire system allows the use of computers and loop-feedback control in piloting aircraft.

Twin-engine vertical stabilisers are big because...

Dutch roll couples oscillations in yaw and pitch

A flying wing uses special control surfaces to both balance and stabilise the aircraft.

Spiral instability is allowed for as long as the diverging period remains long enough for the pilot to respond.