<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/07/25/changing-the-default-button-labels-on-an-alert-control/ -->
<mx:Application name="Alert_noLabel_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white"
        creationComplete="showAlert()" viewSourceURL="srcview/index.html"> 

    <mx:Script>
        <![CDATA[
            import mx.controls.Alert; 

            private function showAlert():void {
                Alert.noLabel = "Non";
                Alert.yesLabel = "Oui"; 

                Alert.show("message goes here",
                        "title goes here",
                        Alert.NO | Alert.YES);
            }
        ]]>
    </mx:Script> 

    <mx:Button label="Alert.show()"
            click="showAlert();" />

</mx:Application>