Apple just released a new firmware update for mid-2012 MacBook Air owners. The release notes say that Apple recently discovered that a small percentage of flash storage drives in these models may have an issue that could cause data loss.
The update, available here, tests your drive and should, if there’s a problem, install new firmware to prevent the issue from happening to you.
If your drive can’t be updated, Apple will replace it free of charge. That’s big news.
All you need to do is hit the firmware download page, download the .dmg file, open it on your MacBook Air, and then run the package file within. It will tell you whether or not your MAcBook Air is supported, and whether you need to upgrade the firmware or replace the drive via Apple.
Source: Apple Support