How to add physics to flight simulator

Hi, I am currently in the process of creating my flight simulator project, very simple, but the main aim of it is to emulate the realistic feel of movement in response to the controls. I have decided to use an xbox controller as the main user controller instead of keys. My plane can fly, and has a camera attached to its front to give a first person perspective, but I have a problem with adding a realistic feel to it by physics (rigidbody), coding wise I'm quite lost in what to do.

 using UnityEngine;
 using System.Collections;
 
 public class PlanePilot : MonoBehaviour {
     public float speed = 90.0f;
 
     private Rigidbody planeRigidbody;
 
     // Use this for initialization
     void Start () {
         Debug.Log ("Plane pilot script added to: " + gameObject.name);
 
         planeRigidbody = GetComponent <Rigidbody> ();
     }
 
     // Update is called once per frame
     void Update () {
 
         transform.position += transform.forward * Time.deltaTime * speed;
 
 
         transform.Rotate (Input.GetAxis ("Vertical"), 0.0f, -Input.GetAxis ("Horizontal") );
 
         float terrainHeightWhereWeAre = Terrain.activeTerrain.SampleHeight (transform.position);
 
         if (terrainHeightWhereWeAre > transform.position.y) {
             transform.position = new Vector3 (transform.position.x, 
                 terrainHeightWhereWeAre, transform.position.z);
         }
     }
 

Sorry for any confusion within the question, my code so far is very basic as you can see so any help would be perfect. Thanks.

-Andre