What version of Mac OS X is pre-installed on the MacBook Air models? Can it run older Mac software?

The precise version and even build number for Mac OS X originally pre-installed on every MacBook Air is provided on the specs page for each model. However, the basic version of each series also is provided below for your convenience:

MacBook Air Series	Original Version of Mac OS X
Original	OS X 10.5 "Leopard"
"Late 2008"	OS X 10.5 "Leopard"
"Mid-2009"	OS X 10.5.7 "Leopard"
"Late 2010"	OS X 10.6.4 "Snow Leopard"
"Mid-2011"	OS X 10.7 "Lion"
"Mid-2012"	OS X 10.7 "Lion"

Versions of the operating system earlier than the one that shipped with a particular Mac are not compatible.

MacBook Air models running Mac OS X 10.5 "Leopard" or Mac OS X 10.6 "Snow Leopard" are capable of running essentially all Mac software written for Intel-based Macs and the vast majority of Mac OS X applications written for PowerPC-based systems using the "Rosetta Universal Binary Translator".

MacBook Air models running Mac OS X 10.7 "Lion" or Mac OS X 10.8 "Mountain Lion" -- whether pre-installed or otherwise -- are not capable of running Mac OS X applications written for the PowerPC processor as this version of the operating system does not support Rosetta.

Mac OS 9/Classic applications are not supported on any version of Mac OS X that is compatible with the MacBook Air line.

Also see:

• What is Rosetta? What does it support?
• What applications are not compatible with Mac OS X 10.7 'Lion'? What upgrade or substitute options are available for common incompatible applications?
• Are there any third-party programs to run Mac OS 9/Classic applications on Intel Macs?

How do you install software on the MacBook Air without an optical drive?

The MacBook Air does not have an internal optical drive, and as such, to install software or transfer files from a CD or DVD one has to either purchase the external MacBook Air SuperDrive or use the "Remote Disk" function. Essentially, you can install the "Remote Disk" software on a nearby Mac or Windows box, and then "borrow" its optical drive to install software or transfer software via CD or DVD.

Of course, for Mac OS X 10.6 "Snow Leopard" and later versions of the operating system, Apple would prefer that you buy all software through Apple's own Mac App Store rather than install software via other means.

Nevertheless, additional information regarding "Remote Disk" is available via the Apple Support Site and in the User's Guide for each MacBook Air. It also is worth noting that this can be used to re-install the operating system and use Apple Hardware Test for troubleshooting for MacBook Air models prior to the "Late 2010" line, but some copy-protected CDs, DVDs, and games cannot be installed using this method.

How do you restore the operating system on the "Late 2010" and "Mid-2011" MacBook Air models? Do they really not ship with a restoration CD or DVD?

The "Late 2010" MacBook Air models -- the stock models of which are the MacBook Air "Core 2 Duo" 1.4 11-Inch and "Core 2 Duo" 1.86 13-Inch -- shipped with a USB key that Apple refers to as a "Software Reinstall Drive" to restore the operating system rather than an optical disc.

For the "Mid-2011" and current "Mid-2012" MacBook Air models, Apple went a step further and does not include a physical restoration method at all.

Instead, the operating system has a hidden "restore" partition containing a "Mac OS X Utilities" application that is only accessible upon startup by holding down Command-R. For more information on restoring one of these MacBook Air models, please refer the User Guide (pages 42-51, specifically). Also note that the OS X Lion USB Thumb Drive available for purchase separately will not work with these MacBook Air models.

Apple's decision to essentially start phasing out optical drives on notebook computers starting with the MacBook Air seems to have surprised many, but Blu-ray notwithstanding, optical media has stalled out in both speed and capacity and this decision is only slightly more aggressive than the decision to phase out the floppy disk drive in the original iMac G3/233 in 1998. Those interested in an optical drive can continue to buy Macs that have an internal optical drive (at least for now) or buy an external drive.

Site sponsor Other World Computing sells Mac compatible external optical drives including Blu-ray options.

Also see: Why did Apple remove the floppy from the iMac G3? Why not include a Zip disk?

Can the MacBook Air play DVD movies via remote disk from another computer?

No. Unfortunately, it is not possible to play DVD movies -- or other optical media (CDs or games) -- that have copy-protection via Remote Disk from another computer.

Can the MacBook Air run Windows? Can you install Windows without the external optical drive?

Like all other Intel-based Macs, the MacBook Air is capable of running Windows. However, it is not possible to install Windows using Boot Camp via Remote Disk, and as such, an external optical drive is required to install Windows on the MacBook Air.

For more information regarding Windows on the Mac, please refer to the extensive Windows on Mac Q&A.

Can the MacBook Air run Linux?

Of course. The MacBook Air is capable of running a number of Intel-based distributions of Linux through Apple Boot Camp or by using "virtualization".

For more on Boot Camp and Virtualization, please refer to the Windows on Mac Q&A.