when your keyboard and touchpad are not working, try to connect an usb mouse and keyboard to the laptop, just to be sure the system is responding.
if the usb devices work, you can be pretty sure there is an hardware problem. if the usb devices don't work too, maybe the system got stuck, and the best thing to do is a system reset
How to Restore MacBook Air to Factory Settings
if the usb devices work, give a try to the apple hardware test to see if it detects anything.
Using Apple Hardware Test
i had a similar problem a few years ago.. if it's an hardware problem you will need to change all the top case
MacBook Air 13 Top Case eBay