- Reset SMC by following the directions applicable to your MacBook Air here ➔ How to Reset SMC. If that does not solve things then-
- Reset NVRAM/PRAM by following the directions applicable to your MacBook Air here ➔ How to Reset NVRAM/PRAM. If that does not solve things then-
More than likely, the above may not resolve the issue because I believe that, based on your findings, your backlight to the display panel is out. Often this happens from a failed IC (Inverter Chip) or a damaged Display Panel Ribbon or a failed fuse link. Any of those can cause the backlit panel to fail. Questions - Did you happen to accidentally drop or bang the MacBook Air? Is the lid opening and closing feel normal to you? Finally, any chance that your MacBook Air may have had some water/liquid damage?
If recommendations 1 and 2 do not work then the next step is to have your MacBook Air examined and if the repair centers are close then please contact ➔ Apple Support
Axel F.