Q: MBA mid 2011 2.9 Firmware update just killed by Air

No. There is no official supported mechanism. The update should be ignored till a fix is available. Applying it just makes things worse.

I am experiencing the wifi issue from sleep, everytime the computer wakes, I have to re-point it to my known WiFi networks after applying EFI update.  *sigh* I hope they fix this quickly as I really was hoping to install the 10.10 beta today, which I will now be re-thinking until this is resolved.

Thanks! I was also having the WiFi issues after the failed update, but a shutdown and restart fixed it for me.

That means firmware update failed.

Me too.

I checked the system information.

The firmware version as same as before.

Exactly the same experience as all you guys.

Tried to update, got a black screen then a restart, saw that the update was still available.

Then my laptop starts not being able to connect to WiFi after sleep.

shutdown my laptop (power off) and start up again and it seems no worse for the wear.

MBA 2011, 11", 64 GB

Boot ROM Version:    MBA41.0077.B0F

SMC Version (system):    1.74f4

Same thing with me. I downloaded the update, installed it, and when the update was (presumably) ready to install, the machine shut down instead of rebooting and has refused to start ever since. No key combination I've seen yet has persuaded it to start up. It's thoroughly bricked. I have a Genius Bar appointment tonight; if they come up with something novel I'll post it.

It seems like that my Macbook Air now (after the EFI Update failed) needs a lot more time to shut down :-(

Really not a good thing.

As noted, the update MUST be ignored if you want a fully functional system.

Various level of degradation, from minor irritation to major angst result if that is NOT the case.

Hmm, my 11 inch MBA, after trying to install the recent toxic update, has escaped with no apparent ill affects. However, I do have a sinking feeling something may yet emerge. Above all, the one hour unresponsiveness of my MBA has severely shaken my faith in Apple's updates. I have long waited a few weeks before updating OS', and now intend to similarly wait with updates. Apple needs to do better!

You may encounter random sleep-wake issues or wifi connections being dropped with the buggy 2.9 EFI Update. 

I wonder why is Apple taking so long to acknowledge and fix the buggy 2.9 EFI update, specially since so many users have reported the failed installation and subsequent problems.

Apple have pulled the update and the download page is no longer available. They should execute a better and through set of tests, before the next update.

That URL to a support page no longer exists - gets a 404 instead.

My Macbook Air doesn't have integrity issues described here in this thread but the WiFi connection has issues now never before seen.  I can see my router but I have to manually select it from a list now to get a connection following a sleep episode (turns off WiFi).  I suspect that the EFI firmware version 2.9 has an issue handling WiFi.

I have already mentioned the WiFi sleep issue before. One more issue I see is that when the MBA wakes up from sleep, it takes a solid 4-5 seconds before the time is updated. Until then the time of the previous sleep is seen. Does anyone else see this too? This is not always the case, but typically after extended sleep time (say overnight).

Needless to say, this has been one botched update from Apple - they need to put more resources in the QA before the release.

The firmware is implementing an aggressive approach to battery conservation. It drops wifi connections (put radio to sleep), the display updates are slower (date/time). There have been issues with IP allocation (on DHCP machines) where it takes a while for the interface to wake up and try to renew IP leases. I have also seen IPSec VPNs being dropped because the physical layer connection was severed. 

Small, lighter devices put more pressure on battery management, due to lower charge capacities. Some tweaking is possible. For example, if the power adapter is connected, the IPSec VPN stays up.

Shorter QA cycles with aggressive time-to-market will always cause issues. /var/log/install.log can provide a historical list of software update frequency.

The Free 10.9.x updates are eventually very expensive for customers.