Gray screen still occurs. Cant' display the option in logging on?
Need help.. No display on screen once power button is on. Gray screen only?
MacBook Air (11-inch, Mid 2012)
Either the drive is failing/failed, the OS is corrupted or you have some other hardware problem.
As to the OS and or drive you can try to start from the Recovery HD partition. Hold down the Command+r keys at startup. If that does not boot then it is either a drive failure or some other hardware problem. With either you need to take the system to Apple to be fixed for free under the warranty.