4 
2 Mabook Air 2014 Network preferences says Wifi No hardware installed
Problem. MB Air suddenly says WIF: NO HARDWARE INSTALLED. Can't turn it on in System Prefs. The hardware doesn't show up in Sys Profile. OSX Mojave. Opened the computer and the cables seem solid. Bluetooth works fine though. They're on the same card so if wifi was a hardware problem wouldn't Bluetooth fail too? Hope to find easy solution before buying new card! Thanks.
Update (08/17/2022)
Sorry. Should've also said I tried resetting SMC and PRAM but nothing helped. I detached and reattached the Airport card cables just to make sure they're connected, but it didn't help. The problem appeared out of the blue. Wifi was working fine, now the Airport card isn't recognized.
971 
Which do you have the 11" or the 13"
Dan さんによる
I have a 13" Air 2014 model with i7 processor 8GB RAM 256GB SSD. Running Mojave 10.14.1
I swapped out the Airport/Bluetooth board with another one. No change. Still "no hardware installed".
Bluetooth works fine.
Ideas?
I'll erase the disk and reinstall, starting with Sierra, then upgrading as needed.
Simple Simon さんによる
Lets give this a try, go into your AirPort settings and delete the saved networks then restart you system, then rejoin your WiFi network (don't forget the AP's names cAsE and its password before you loose them).
Dan さんによる
Problem is I don't have any Airport settings. In the Network preference pane there is no Airport interface and if I click on the + to add a new service the options are Thunderbolt interface, etc. , but not Wifi. It's as if there's no Airport card installed. But there is, I just swapped in a new one, and Bluetooth works fine.
Simple Simon さんによる