Stop Alpha fade loop

I have a bit of ActionScript for an image alpha fade, but for some reason it loops. After a while, the picture that fades up disappears, then cycles through again. Does someone know a way to have this script not loop?

this._alpha = 0;
this.onEnterFrame = function() {
if (this._alpha == 100) {
delete this.onEnterFrame;
} else {
this._alpha += 30;
}
};