Q: Can I download Windows 8 directly onto Macbook Air?

Here is how to install Windows 8 on a Mac:

http://support.apple.com/kb/PH11131

Hopefully this answers your question:

________

Can I use a downloaded (ISO) version of Windows with Boot Camp?
MacBook Air (Mid 2011 and later), MacBook Pro (Mid 2012 and later, including Retina models), Mac mini (Mid 2011 and later), and iMac (Late 2012) can install downloaded (ISO) versions of Windows 7 and 8.

To determine if your Mac supports this feature:

1. Click the Go menu and choose Utilities.
2. Open Boot Camp Assistant.
3. Click Continue. If you see a "Create a Windows 7 or later install disk" checkbox, your Mac supports the use of downloaded (ISO) install images. See the Boot Camp Installation & Setup Guide for more information.

___________

The above comes from here:

http://support.apple.com/kb/HT5639