This article discusses several ways to restart a MacBook Air, reasons why you might want to restart a MacBook Air, and how to force restart a frozen MacBook Air.
HOW to factory reset your MacBook Air [09-17]
Probably the easiest way to reboot a MacBook Air is to click through a few menus that you can access from almost any screen. Here's how:
Click the Apple menu in the upper-left corner of the screen, then click Restart.
To ensure that all apps and documents reopen after restarting, check the box next to Reopen windows when signing in again.