Just in case you’d like to use AirPort Utility 5.6.1 on Mountain Lion (and probalby Lion as well), here’s how to install it:
1. Download the disk image (its here: http://support.apple.com/kb/DL1536).
2. Mount the disk image and drag the install package (AirPortUtility.pkg) to your desktop.
3. Fire up Terminal and prepare to show off…
4. Make a temporary directory and cd into it: mkdir tmp ; cd tmp
5. Extract the Payload file from the install package with xar, here’s the command: xar -x -f ~/Desktop/AirPortUtility.pkg Payload
6. The result will be a directory named AirPortUtility.pkg (just like the file, but now you can move into it to get the files you want). Inside will be a file called Payload that is a compressed archive of AirPort Utility.app.
7. So our next move is to extract the app. Here’s the command: gzcat AirPortUtility.pkg/Payload | tar -xf –
8. When it finished there will be three new folders Applications, Library, and System. Your nice new copy of AirPort Utility 5.6.1 will be in the Utilities folder inside of the Applications folder. Use Finder to rename it (assuming you want to keep version 6 as well) then drag it to your Applications/Utilities folder.
9. The other two folders hold the AirPort Base Station Agent and its supporting files. I’m not sure if you need/want these or not. As best I can figure the agent does two things: it checks for updates for AirPort Utility and it monitors AirPort base stations for problems. You probably already have a version running as it comes with the system and it seems to know how to talk to both versions of AirPort Utility (I got nagged about updating).
10. The final step is to launch AirPort Utility and confirm that it works. You’ll probably want to go into preferences and turn off the option to check for updates. If all is good you can remove the temporary directory: cd .. ; rm -rf tmp (or drag it into the trash with Finder).