It seems like every IT security article you read indicates that defensive barriers are becoming more and more effective.  This is such a case, but a closer read of the scenario reveals that a strong layered defense would protect an air-gapped device for the simple reason that some form of malware must be present.

http://arstechnica.com/security/2016/08/meet-usbee-the-malware-that-uses-usb-drives-to-covertly-jump-airgaps/