Make GameObject move at the same x axis as the player?

Scripting
1

Hi
I have a FPS Controller set up my scene and a Plane. I want the plane to move on the same x axis as the player, but not on the z and y axis. How could I do this? Here’s a script I have that that makes the player rotate on the same y axis as the camera when an input is held. Maybe someone could change it a little to make it do what I’m trying to accomplish…

#pragma strict
@SerializeField
var aimSpeed : float;
function Update () {
    if (Input.GetButton("Aim"))
        Aim();
}
function Aim() {
    var aimRotation : Vector3 = transform.rotation.eulerAngles;
    aimRotation.y = Camera.main.transform.rotation.eulerAngles.y;
    transform.rotation = Quaternion.Lerp(transform.rotation, Quaternion.Euler(aimRotation), Time.deltaTime * aimSpeed);
}

Thanks if you can help!

2 
var movement : Vector3 = new Vector3(playerTransform.position.x, planeTransform.position.y planeTransform.position.z);

planeTransform.position = movement;