My MacBookAir is freezing. How can I get it working?

1)  Apple Laptops are downloading and installing updates in the background. Since deploying the SBAC MacBook Airs, there have been two major OS updates. One was released 4/8/15 [see https://support.apple.com/en-us/HT204490] and it was over 2GB. Once the computers begin the process there is no way to stop it without the possibility of OS/data corruption. The solution in this instance is to turn the computers on, make sure they are connected to the wireless network, and let them run for at least 30 minutes.  

2) If your Mac appears to be running normally but isn't responding, force the computer to shut down by pressing and holding the power button for 10 seconds

OR

You can Force Quit the Finder by opening the Force Quit pane (Command + Option + esc) and scrolling to the bottom of the box, choosing Finder, and clicking on the Force Quit button at the bottom of the pane.

You can also reset the NVRAM

1. Shut down your Mac.
2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. 
3. Turn on your Mac.
4. Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
5. Hold these keys until the computer restarts and you hear the startup sound for a second time.
6. Release the keys.

 If these do not work, please review this article to reset the SMC (System Management Controller)  https://support.apple.com/en-us/HT201295