The MacBook Air is an ultra-portable Mac notebook computer. When a computer stops responding to commands or the cursor will not move, the application or computer may be “frozen.” If an application freezes, you can reset the MacBook Air by using the "Force Quit" function. If all operations on the computer are frozen, you can reset the MacBook Air by manually shutting down the computer.
Press the “Command,” “Option” and “Esc” keys on the keyboard at the same time to bring up the “Force Quit Applications” window.
Click the application that is not responding and click “Force Quit.” If this succeeds, close any other open applications and restart the computer. If it does not, continue to Step 3.
Press the power button and hold it down. Release the button when the MacBook Air shuts down.
Wait a minimum of 10 seconds and press the power button to restart the computer.