WARNING: This was written for a BETA version of AIR and may not be valid for the most recent release
Note: The AIR Update for Flash CS3 is currently in beta meaning the following information is subject to change.
The AIR Update for Flash CS3 allows you more easily create, test, and distribute AIR applications in Adobe Flash CS3. If you are not creating AIR applications, or have no intention of creating AIR applications with Flash, you will not need this update. This update is also not required to produce AIR applications in Flash. However, it does make it a lot easier.
As it exists now, for example, Flash CS3 does not contain the definitions required (stored in SWC files) to identify classes and definitions that are unique to the AIR runtime. If you attempt to import or use these classes in a Flash CS3 file, you will more than likely encounter errors when you publish your SWF.
Also, if you are developing for the AIR runtime with Flash and wish to test your application, you cannot do so within the Flash authoring environment. Testing your application there only runs the SWF within Flash's native external Flash Player; it does not use AIR. This means, in order to fully test your movie, you have to first publish your SWF and then manually run it in the ADL of the AIR SDK.
By installing the AIR Update for Flash, you not only get the AIR SWC necessary to recognize AIR-specific definitions, but you can also use Flash to create AIR specific documents and publish them directly to ADL. ADL is the AIR Debug Launcher, a program for running AIR projects without needing to install them (used for development and included in the AIR SDK).
Note: In order for the Output panel to receive trace statements from ADL, you will want to test your movie using Debug > Debug Movie.
Additionally, after installing the AIR update, you will have two new AIR commands in Flash's Commands menu. These commands include AIR - Application and Package Settings and AIR - Package AIR File.
The Application and Package Settings opens a new dialog that allows you to edit common properties of the current AIR application. These properties are saved in a <FLA filename>-app.xml file serving as the AIR application descriptor file. AIR applications rely on the application descriptor file (or application XML) when an AIR application is launched and even when packaged into a distributable AIR installer.
The Application and Package Settings dialog also lets you define what additional files are to be included in your AIR installer package. These files will be packaged when you use the Package button in the Application and Package Settings dialog or when you use the other AIR command, Package AIR File. A .air file with the specified name will be added to your FLA's directory ready for distribution.
In its beta state, this update does not include documentation for AIR classes in Flash help. For AIR-specific documentation, you will have to rely on the Flex 3 language reference currently available on the Adobe Labs livedocs.
The properties available for edit in the Application and Package Settings dialog also consists of a subset of features that can be added to the descriptor file. If you want to use a custom application XML file, you can do so by specifying that file in the same dialog. Note: if a custom file is used, it should have a name different than that of the one generated automatically (<FLA filename>-app.xml). More information on this file can be found with other documentation such as in the AIR SDK.
You can currently download the AIR update for Flash CS3 Professional from the Adobe Labs. The download page also contains additional information such as system requirements and known issues. There are no special requirements for installation. Just install as you would any other application and restart Flash.
Once the update is installed, you can change an existing ActionScript 3 FLA to publish to AIR within the publish settings dialog.
You can also create a new AIR application from the Welcome Screen when you first open Flash which will create a new ActionScript 3 FLA already set to publish to AIR.
Adobe labs has more information about using AIR update.
For anyone developing for AIR using Flash CS3, this update is a necessity. It's an easy to install, free update that will get you on your way to quickly and easily developing AIR applications with minimal hassle.