How to make a space ship fly after crosshair?

I'm trying to make a game like this: https://www.youtube.com/watch?v=YXWx0H8mZM0 but I can't make my space ship fly in the direction that I point my mouse towards (crosshair). I've tried to use different scripts but I can't make anything work... I've been stuck at this for at least 2 hours now :/

using UnityEngine; using System.Collections;

public class LookAtMouse : MonoBehaviour {

 public GameObject player;
 // speed is the rate at which the object will rotate
 public float speed;

 void FixedUpdate() {
     // Generate a plane that intersects the transform's position with an upwards normal.
     Plane player = new Plane(Vector3.up, transform.position);

     // Generate a ray from the cursor position
     Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);

     // Determine the point where the cursor ray intersects the plane.
     // This will be the point that the object must look towards to be looking at the mouse.
     // Raycasting to a Plane object only gives us a distance, so we'll have to take the distance,
     //   then find the point along that ray that meets that distance.  This will be the point
     //   to look at.
     float hitdist = 0.0f;
     // If the ray is parallel to the plane, Raycast will return false.
     if (player.Raycast(ray, out hitdist)) {
         // Get the point along the ray that hits the calculated distance.
         Vector3 targetPoint = ray.GetPoint(hitdist);

         // Determine the target rotation.  This is the rotation if the transform looks at the target point.
         Quaternion targetRotation = Quaternion.LookRotation(targetPoint - transform.position);

         // Smoothly rotate towards the target point.
         transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, speed * Time.deltaTime);
     }
 }

}