updated 05:37 pm EDT, Wed July 30, 2014
Previous update caused system crashes, unstable or unbootable machines
Apple released a new update for MacBook Air EFI firmware today, updating to version 2.9.1 for "Mid-2011" models of the notebook. The company states that the update fixes a few issues for owners facing problems with waking from sleep and fans running at full speed in a specific instance. The update replaces a previous version that caused a number of additional problems for owners.
Update 2.9.1 sets out to correct a rare issue MacBook Air owners were having with cooling fans kicking into full speed after the machine came out of sleep. It also fixes a problem where the MacBook was taking too long to wake from sleep. Users must be running OS X 10.9.2 or later to be able to apply the update.
The previous version of the firmware update that was released earlier in the month caused problems for MacBook Air owners attempting to install it. A support thread on Apple's website listed a number of issues users faced after attempting to install the update. The thread sits at 140 replies and over 8,000 reviews as of today. The 2.9 update was only listed as being compatible with four EFI versions, while the new update covers only MBA41.0077.B11 (the previously-updated firmware version) as needed.
Problems ranged from small issues like the machines taking one to two hours to reboot to complete the process or the App Store still showing the update, to much larger issues crashing the entire MacBook Air. In a few cases, SMC resets were required to get the notebooks up and running again, but left users in the same situation of not being able to apply the update.
Some owners found success with the firmware update, but reported stability issues afterward. It's believed the system problems were tied to a bad install file rather than a bug in the update itself.