Apologies if my answer is not applicable to your MBA as I have an late '11 MBA.
But for my MBA, the above answers would be incorrect. Actually, they're technically worse than incorrect but it's not that important. To properly 'erase' all data from an SSD, you need to boot into a Linux distribution from an external drive (USB or SD or CD), open a Terminal and get to root however you prefer - I use:
$ sudo su -
but if you boot using partedmagic.com (which I think is your best option), you will be automatically logged in as root when you open a Terminal.
# hdparm -I /dev/sda
This is to determine if your SSD is "locked" and it likely would be; at which point things will either be difficult or very easy. If it's locked, see below. If it's not locked, it's easy:
# hdparm --user-master u --security-set-pass Eide /dev/sda
(this is to 'lock' your drive for the ATA Secure Erase command, the "Eide" password can be another password of your choosing)
# hdparm --user-master u --security-erase Eide /dev/sda
Though for the life of me I cannot understand the difference between "Secure Erase" and "Enhanced Secure Erase" (especially as they are both completed in mere seconds (with Enhanced actually slightly faster, but I'm sure that's not the reason it's 'more' Secure than Secure (go figure), what I do is - quite simply - to do both:
# hdparm --user-master u --security-set-pass Eide /dev/sda # hdparm --user-master u --security-erase-enhanced Eide /dev/sda
You can add --verbose to all of those to get more information, but I'd be lying if I claimed to have a clue about the output ;)
Now if your SSD is locked (and I imagine it will be), you have to get it unlocked somehow which is so much more complicated than it should be. Your best bet is to download Parted Magic and click Start > System > Erase and it will open a GUI menu showing your available drives, select your SSD hard drive, confirm the next screen, and then it will offer you the option to put the drive 'to sleep' - which is easy to do on any system but OS X. With OS X there is no guarantee but this thread is probably the best list of options you can try if simply closing your lid for a couple minutes then opening it doesn't put your drive to sleep or if the Parted Magic option to 'sleep' your drive doesn't allow you to boot back into the saved state.
Hope this helps. FWIW the answers above, whilst no doubt well-intentioned, are absolutely incorrect (as you'll quickly discover reading the MacRumours thread above - or even Googling basic SSD facts using search terms like "SSD ATA Secure Erase" etc). gl gl