Although the 6.x version has a number of features that the 5.x had, it is not as complete ... and some of those features can only be had using version 5.x. Both versions will run just fine under Mountain Lion, but version 5.x won't install ... at least not via the traditional sense.
Here are the basic steps to install version 5.6 under Mountain Lion using CharlesSoft's Pacifist:
- If you haven't already download the AirPort Utility disk image file directly from Apple Support Download
- Place the resultant AirPortUtility56.dmg file onto your Mac's Desktop.
- Run Pacifist.
- Click on the Open Package option. Find the disk image file that you just placed on your desktop, and then, click on Open.
- The utility is located as follows: Contents of AirPortUtility56.dmg > Contents of AirPortUtility56.pkg > Contents of AirPortUtility56Lion.pkg > Applications > Utilities > AirPort Utility 5.6.app
- Drag AirPort Utility 5.6.app to your Mac's /Applications/Utilities folder.
You can now run the AirPort Utility from the Utilities folder.