I'll admit this is purely hypothetical, but given that we know many people act on stuff they read on the Internet in an uncritical fashion - we cannot dismiss AI because it "doesn't have access to air gapped systems". A human has access to that system - a superintelligent AI could convince that human to "push the buttons".

I don't actually believe this will happen, but I'm not 100% confident it wouldn't. I don't know what a superintelligence would look like!