Thanks for your reply,
I was asking, because my imagination was running wild in the direction of:
1. AIR executes like a 'regular' application.
2. OS on multithreading machines can assign different CPUs to individual processes.
3. MultiCore PureMVC uses a separate AIR runtime for each of its MultiCores.
One of them has a visible window showing the GUI surface.
The other Cores run in background only.
4. OS assigns a different CPU to each of the PureMVC Cores.
5. PureMVC uses LocalConnections to 'combine forces' of the individual threads.
6. Voila > multithreading AIR application.
But as I said, only my imagination running wild.