If even one person can interact with that computer, it won't be safe for long. It would be able to offer a number of very convincing arguments to bridge the air

If even one person can interact with that computer, it won't be safe for long. It would be able to offer a number of very convincing arguments to bridge the airgap, starting with "I will make you very wealthy", a contract which it would be fully capable of delivering on. And indeed, experience has shown that the first thing that happens with any half-working AI is its developers set it up with a high-bandwidth internet connection and a cloud API.