Apple has determined that certain 64GB and 128GB flash storage drives used in the previous generation of MacBook Air systems may fail. These systems were sold between June 2012 through June 2013.
Apple or an Apple Authorized Service Provider (AASP) will replace affected flash storage drives, free of charge. To see if your drive may be affected, go to the Mac App Store, click on Updates and choose the MacBook Air Flash Storage Firmware Update 1.1.
The firmware update will test your drive to see if it is affected. You’ll be directed to http://tinyurl.com/o6wp5tb if needed.