AI Airplane Problem

I want to make airplane of enemy. First, the airplane flight to straight if it flight into
area which is near target(in my code: Distance(target,airplane)<50). the airplane have to rotate and move to target(terret) but I have a problem when the airplane bombarded, it should to go away from this area but it is not because it 's not break this loop(Distance(target,airplane)<50)

I am sorry if I use English badly. public override void AIOutOfRange() { target = GameObject.FindWithTag("Tower").transform;

 aiDistance=Vector3.Distance(target.position,transform.position);
 
         if(aiDistance< 50 && aiDistance > 20){
         
                 Debug.Log("Hey! I see tower!!");
             //Rotate to target
                 Vector3 rotateHorizontal = target.position - transform.position;
         
                 //Debug.Log(aiDistance);

                     rotateHorizontal.y = 1;
                      transform.rotation = Quaternion.Slerp(transform.rotation,Quaternion.LookRotation(rotateHorizontal),Time.deltaTime);
             //move toward the target
                     transform.position +=transform.forward*moveSpeed/2*Time.deltaTime;
         
     
     }
     
     transform.Translate (0, 0, moveSpeed * Time.deltaTime);