Transfer disk image from one MacBook Air to another
If both MacBook Airs have Thunderbolt, the easiest way would be to use Migration Assistant over Thunderbolt:


Get a Thunderbolt cable (borrow or buy).
Boot the old Air into Target Disk Mode (hold down T while booting).
Connect the MacBook Airs via the Thunderbolt cable.
On initial boot of the new Air, you'll have the option of using Migration Assistant off another Mac. 
Select the types of items you want to copy.
Wait while Migration Assistant does its magic.
Et voilà, your new Air is just like your old one except newer and faster.