Instead of static bitmap, a xml may be used. First, create my_logo.png and my_splash.xml:
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
<item>
<shape android:shape="rectangle" >
<solid android:color="#FFffFFff" />
</shape>
</item>
<item>
<bitmap android:src="@drawable/my_logo" android:gravity="center" />
</item>
</layer-list>
Next, modify styles.xml:
<style name="Theme.NoShadow" parent="@android:style/Theme.NoTitleBar">
<item name="android:windowContentOverlay">@null</item>
<item name="android:windowBackground">@drawable/my_splash</item>
</style>
and lastly, there is a possibility not to touch AIR but to make changes to apk, then to re-sign it (all this is possible with the help of build scripts, using jarsigner and zipalign)