Generally, this is where a framework/microarchitecture comes into play. You have to keep in mind, that the Flex/Adobe Air library is first and foremost a component library. That means you don't get anything out of the box to help with things such as communication between different part of the app. Sometimes folks will try to use the Singleton Pattern to manage dependencies, but I can tell you from experience that is a horrible mistake that will cost you in the long run as the code becomes very brittle and fragile with high cyclomatic complexity.
Nowadays, there are many frameworks designed to help you with the problem and others that you have and will face. A list of these frameworks can be found through Google, but Swiz, Mate, Robotlegs and Parsley is a great starting point.
There are other frameworks that you may run across such as Cairngorm and PureMVC. Those are generally termed "first generation" frameworks. Personally, I shy away from those because they feel a little too heavy an intrusive.