>Apparently, connecting to the airplane wifi (without yet logging in) was enough to satisfy the OS set-up, but limited enough that it didn't require a microsoft account.
Set up a wifi network with no internet? If you have a separate router/modem, just unplug your modem from your router. If your mode/router is combined unplug the coax/fiber/phone line.
Set up a wifi network with no internet? If you have a separate router/modem, just unplug your modem from your router. If your mode/router is combined unplug the coax/fiber/phone line.