SWFLoader can be used to load an external flash movie file into the current stage. All that you need to do is to set the source property of SWFLoader. What's more, if you want to passing additional data to the being loaded swf, try passing the data as query strings.

<mx:SWFLoader source="player.swf?movie=video.flv" />

Well, until now it works fine, but how can we pass more data into the swf? You may do as follows.

<mx:SWFLoader source="flvplayer.swf?movie=video.flv&autoplay=true" />

Oops, the compiler throws an error:
The reference to entity "autoplay" must end with the ';' delimiter.
I don't know what this error means, but I will show two ways to avoid the error. First, use member variable and bindings.

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
	<mx:Script>
		<![CDATA[
		public var source:String = "player.swf?movie=video.flv&autoplay=true";
		]]>
	</mx:Script>>
	<mx:SWFLoader source="{source}"/>
</mx:Application>

The second way, modify source property dynamically in function childrenCreated.

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
	<mx:Script>
		<![CDATA[
	     override protected function childrenCreated():void
	     {
	        super.childrenCreated();
	        player.source = "player.swf?movie=video.flv&autoplay=true";
	     }
		]]>
	</mx:Script>
	<mx:SWFLoader id="player"/>
</mx:Application>

If the swf is played in browser through a html wrapper, the query strings will work. but if it is played in flash player directly, the query strings will not work. AFS will support query strings in version 1.2.