flex/air open link in new window of system browser

 <mx:LinkButton label="Click here  " color="#0000FF" fontWeight="bold"       
                                    click='OpenUrl(event)'  x="55" y="140" width="254" textDecoration="underline"/>


       <fx:Script>
                <![CDATA[
                        import flash.net.*;
                        import flash.system.*;
                        
                        protected function OpenUrl(event:MouseEvent):void
                        {
                                navigateToURL( new URLRequest( "http://sourcefield.blogspot.com"));
                        }