ActionScript 3.0 :: Simple Vertical Plane Shooter - HitTestObject

I've been trying to work on this simple vertical plane shooter. I got as far as creating everything and am now on the step to check if my bullet hits an enemy plane or an enemy bullet hits my plane. Because the enemy planes are created dynamically, I am trying to counter that with assigning then names when created so that the bullet knows what to look for. My approach for this might be somewhat wrong though. As for the enemy bullet hitting my plane, I just tell it to look for the instance of the plane already on the stage. Both result in the same error of undefined(the object can't be found).

Here is the code for both bullet collisions and the code for creating enemies.
ActionScript Code:
public function enemyHit(e:Event):void {
//declare i
var i:int;
//check if the bullet hit any enemy object
for(i = 1; i <= MovieClip(root).amount; i++) {
if(this.hitTestObject(enemy + i)) {
trace("enemy hit");
[Code] .....

The bullets have their own class files and the spawn enemy code is located within the fla file.