Rotate object (plane) with lerp back to start?

I am making a simple game where you are a bomber plane and i want to rotate the the plane slightly when flying left or right. It will rotate, but not go back. I will also need to replace yield return new WaitFor seconds with something with on key release

public GameObject plane;
public GameObject WingTarget;
public GameObject westWingStart;
public GameObject westWingEnd;
public GameObject eastWingStart;
public GameObject eastWingEnd;

// Use this for initialization
void Start () 
{
	
}

// Update is called once per frame
void Update ()
{
	if (Input.GetKeyDown(KeyCode.A)) 
	{
		StartCoroutine (WingTurn());
	}

	if (Input.GetKeyDown(KeyCode.D)) 
	{
		StartCoroutine (WingTurnE());
	}

	plane.transform.rotation = Quaternion.Lerp(plane.transform.rotation, WingTarget.transform.transform.rotation, 0.25f);

}

IEnumerator WingTurn()
{
	WingTarget.transform.rotation = westWingEnd.transform.rotation;

	yield return new WaitForSeconds (0.05f);

	WingTarget.transform.rotation = westWingStart.transform.rotation;
}

IEnumerator WingTurnE()
{
	WingTarget.transform.rotation = eastWingEnd.transform.rotation;

	yield return new WaitForSeconds (0.05f);

	WingTarget.transform.rotation = eastWingStart.transform.rotation;
}

}
WingTarget, westWingStart, westWingEnd, eastWingStart, eastWingEnd; are all children of the plane. the starts have a rotation of 0 and the ends have a rotation of x -30 and 30 respectively.

In your update function trying using this…

if (Input.GetKeyUp(KeyCode.A)) 
     {
         StartCoroutine (WingBack());
     }

if (Input.GetKeyUp(KeyCode.D)) 
     {
         StartCoroutine (WingBack());
     }

Make an co-routine function WingBack which will set the rotation of wings back to their initial rotation…