No flex
Yes, it is possible on iOS without using Flex. This process involves placing the default image at the root of your project.
More detailed information can be found here:
http://help.adobe.com/en_US/air/build/WS901d38e593cd1bac1e63e3d129907d2886-8000.html#WS901d38e593cd1bac58d08f9112e26606ea8-8000
On Android, I don't think there is a similar bit of functionality. I believe this is trying to get closer:
http://swfhead.com/blog/?p=817
Flex
Flex SDK , :
<s:ViewNavigatorApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
splashScreenImage="@Embed('spash.png')"
splashScreenScaleMode="letterbox">
Flex 4.6, .
SpashScreenImage.mxml:
<s:SplashScreenImage xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark">
<s:SplashScreenImageSource dpi="160--" aspectRatio="portrait" source="@Embed('portrait.png')"/>
<s:SplashScreenImageSource dpi="160--" aspectRatio="landscape" source="@Embed('landscape.png')"/>
</s:SplashScreenImage>
:
<s:ViewNavigatorApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
splashScreenImage="SpashScreenImage">
:
http://devgirl.org/2012/01/20/flex-mobile-development-dynamic-splash-screens/