Making use of the Grid container
<?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:Grid> <mx:GridRow> <mx:GridItem> <mx:Button label="A" /> </mx:GridItem> <mx:GridItem> <mx:Button label="B" /> </mx:GridItem> <mx:GridItem> <mx:Button label="C" /> </mx:GridItem> </mx:GridRow> <mx:GridRow> <mx:GridItem colSpan="3"> <mx:Button label="STOP" width="100%" /> </mx:GridItem> </mx:GridRow> </mx:Grid> </mx:Application>