how to move an object in a curved way

thanks for the reply i will chek and revert bak here asap

Vector3.SmoothDamp still makes the plane turn at once! i need the plane to make a sort of a curve while it is turning !

achieved the curved turning of aircraft.the way i used is so simple i.e., made my aircraft to follow an cube.(cube will move in the user given path and my aircraft follows the cube)here cube and aircraft are separated with an distance. hence when cube turns at turnings aircraft also turns but with a curved way(with an offset).i used ai controller for both cube and aircraft movement.thanks for all for giving suggestions.thanks unity

Try Vector3.SmoothDamp, and change the target point when you're under a safe distance of it, like one or two.