Changing the spawn rate

Hi, I wanted to know if anyone could help me with this code. I am trying to change the spawn rate through the use of arrays. However, I am having problems the code below makes the planes spawn at the same time and same distance to the level. How do I edit this to make it appear more random?

Thanks.

function Start () { gather_spawners(); }

function Update () { spawn_new_plane(); }

private var spawners = new Array();

var plane : GameObject;

private var spawnDelay : float = 1.0; private var timeToSpawn : float = 0.0;

function spawn_new_plane() { if(Time.time > timeToSpawn) { // Choose a random spawn point (from the spawners array)

var rNum : int = Random.value * spawners.length;

var randomSpawnPoint : Transform = spawners[rNum];

Instantiate(plane, randomSpawnPoint.position, randomSpawnPoint.rotation); timeToSpawn = Time.time + spawnDelay; }

}

function gather_spawners() { var potentialSpawners : Array = GetComponentsInChildren(Transform);

 for (var potentialSpawner : Transform in potentialSpawners) {
     if(potentialSpawner != transform) {
         spawners[spawners.length] = potentialSpawner;
     }
 }
 Debug.Log("SL: " + spawners.length);