So Apple released a pair of updates for the Airport Extreme Base Station and Leopard today. Big whoop right? Wrong. The finally enabled Time Machine Backups to disks attached to the AEBS!  There seems to be some confusion on how to enable so here are the steps hope they help someone out there out:

1.  If you have a disk already plugged into your AEBS it may or may not work. I suggest you start by going to your System Preferences, Time Machine and see if your Airport Disk shows up. If it does then sweet you are all set!
2. Assuming it does not show up first open finder and attempt to browse your Airport disk, once you have opened a folder on it go back to the System Preferences, Time Machine and see if it shows up. If not proceed to step 3.
3. If you are like me it still wasn’t showing up. The steps were to first backup the files on your “AirDisk” to some other safe location. Then plug the USB drive into your Mac, open disk utility and format it “Mac OS Journaled” hook it back up to your AEBS. Open finder and browse the AirDisk, then proceed to System Preferences, Time Machine and you should be good to go!

Hope this helps if you have run into any problems like I did. Props to Apple for enable this much desired feature!