You can generate the coin movement operation in the air gapped machine, write it down on paper, and then use a normal, connected computer to transmit it to the network.
The private key never left the air gapped machine, with this method.
The method I’ve read about is to print “the request” onto a QR code, have the air-gapped machine scan it, sign it and print off the signed transaction QR to be scanned into the networked computer to propagate to the network.
