As a tech blogger, I can't provide an exact answer to this question without more information. However, I can assume that you are referring to the auto-lock feature that's available on MacBook Air. By default, a MacBook Air will automatically lock itself after a certain amount of time has passed without any activity. This time can be customized by going to System Preferences > Security & Privacy > General. Here, you can set the amount of time that needs to elapse before the computer automatically locks, ranging from immediately to up to 1 hour. The time that it takes for a MacBook Air to lock will depend on the setting that you have chosen.