MacAIR keyboard light won't light up automatically

Good morning Otabek_USA,

If your MacBook Air's keyboard backlighting is not behaving as it should, I would suggest that you reset the computer's System Management Controller. Use the steps in this article -

Intel-based Macs: Resetting the System Management Controller (SMC) - Apple Support

Specifically -

Resetting the SMC on portables with a battery you should not remove on your own

Note: Portable computers that have a battery you should not remove on your own include MacBook Pro (Early 2009) and later, all models of MacBook Air, and MacBook (Late 2009).

1. Shut down the computer.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer.
   Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC

Thanks for using Apple Support Communities.

Best,

Brett L