MBA displays the Question mark Folder on booting up All of a sudden MBA boots displaying question mark folder. I've tried booting from a USB OS X to use disk utility but can't see the Macintosh HD of the Air to fix the disk. Safe mode doesn't seem to work. Any root-cause? Any solution?
The question mark folder usually means:


The hard disk is failing or has failed
Your Mac can't find a System Folder to boot from


Try starting up while holding down the Alt/Option key. That should prompt the Startup Manager window where you can select the startup disk.



If that doesn't help, refer to this Apple KB Article.