Workers adds concurrency in flash, but they are hard to use and maintain. I solve this problem with mvcExpress v2 framework extension for workers!
mvcExpress worker extension will let you create background workers with one line of code, automatically set up communication between them for you to use, and it will automatically register your class aliases for your custom objects to be typed then sending between workers.
Example project ZIP download: http://goo.gl/a4yY5J
Framework homepage: http://mvcexpress.org/