Try, Sothink Decompiler
I am not sure you will recover a FLA that would have been the same as the FLA that has been used to compile your SWF.
You may get some objects, graphics, and scripting but some things may be missing or different.
The SWF is a compiled version into a core language of the original FLA. The compiling get rid of a lot of stuff or arrange things its very own way.
Where I want to go is : don't look for the perfect reverse-engineering program. You should better work on a new FLA and import what you have recovered from the conversion of the SWF.
Thanks for the answer.
I have tried this one but Action Script disappears when I save it. Any more suggestions?
Thanks for your answer.
I wish I could create a new one but I did it years ago and I can't remember how to make a new one now...