If you really need an air gapped computer, wouldn't it make a whole lot more sense to build a desktop with some variety of ATX form factor motherboard that you can examine in detail to confirm that it has zero wireless functionality?
A Macbook Air, which is pretty much designed as a wifi-dependent network terminal, would be way down my list of hardware I would choose if I had to build an airgap lab environment.
I would start with a Librem laptop as this is exactly the point of them. Hopefully all you'd have to do is verify the killswitch works as advertised. disclaimer: typing on one now.
A Macbook Air, which is pretty much designed as a wifi-dependent network terminal, would be way down my list of hardware I would choose if I had to build an airgap lab environment.