Why is Wi-Fi hardware not recognized?

Hey there!

A friend gave me an old Macbook Air with networking problems, with the question if I could fix it for her. The problem is: the laptop cannot connect to Wi-Fi. The Wi-Fi icon does not show up in the top bar. When I go to 'System Preferences' then to 'Network', and click the '+' icon, 'Wi-Fi' does not show up as an option under 'Interface'. The only options there are 'Bluetooth PAN', 'Bluetooth DUN', 'VPN', 'PPPoE' and '6 to 4'.

Even when I go to 'About this mac' , then to 'System report' and then to 'Wi-Fi' under the 'Network' tab, I only see some software specifications. It seems no Wi-Fi hardware is recognized.

As far as I know, the original owner already reinstalled Max OSX. I have also tried to reset NVRAM and the SMC, but this had no effect.

Is there anything I can do to fix this issue? Is the next step forward to replace the networking card? Or are there more steps I should take to make sure whether that is the problem?