How can I make my airplane tilt?

I have an airplane and I am trying to make it tilt when I turn left right, up down, however, I don’t know how to do that, and I have looked around quite a bit, but nothing has worked.

Here is what I have so far:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerMovement : MonoBehaviour
    void Update ()
        Rigidbody rb = GetComponent<Rigidbody>();
        if (Input.GetKey(KeyCode.A)) rb.AddForce(Vector3.right);
        if (Input.GetKey(KeyCode.D)) rb.AddForce(Vector3.left);
        if (Input.GetKey(KeyCode.W)) rb.AddForce(Vector3.back);
        if (Input.GetKey(KeyCode.S)) rb.AddForce(Vector3.forward);
        if (Input.GetKey(KeyCode.Space)) rb.AddForce(Vector3.up);
        if (Input.GetKey(KeyCode.LeftShift)) rb.AddForce(Vector3.down);

A bit rusty with Unity, but I think you’ll need to create a new float variable called ‘force’ or something, and then in your update, use AddTorque instead of AddForce (at the moment I assume that your plane slides rather than turn).

if (Input.GetKey(KeyCode.A)) rb.AddTorque(-force);
if (Input.GetKey(KeyCode.D)) rb.AddTorque(force);

I think anyway.