Yes or you could also lock it, then the next time it goes on the internet it will get locked or erased. If you erase it, you just gave it to them more or less as they will have full use of it at that point.
But this will only work if they have not erased the hard drive and installed a fresh OS.
Did you have the efi password set? Not would have kept them from erasing the unit and getting pass the lock screen. Not an easy fix without the know-how
If not, it may be to late as it could have been erased.
This is why I tell folks to efi lock their device and use something other than a short four digit number.
This way the thief cannot simply use a teensy 3 device to automate all 10,000 possibilities.
btw:
What year model is your air, older models are not as secure.
