Apple has patched a issue which effected new MacBook Air displays, in which 11- and 13-inch models, and resolves a rare issue where MacBook Air boots or wakes to a black screen or becomes unresponsive.
“The MacBook Air EFI Update will update the EFI firmware on your notebook computer. Your computer’s power cord must be connected and plugged into a working power source. When your MacBookAir restarts, a gray screen will appear with a status bar to indicate the progress of the update. It’ll take several minutes for the update to complete. Don’t disturb or shut off the power on your MacBookAir during this update.
Boot ROM or SMC Version Information: After this update has successfully completed, your Boot ROM Version will be: MBA31.88Z.0061.B01.1011181342,” explains Apple in KBDL1337.