Wouldn't be so sure. Data is eventually copied out of the airgapped side, e.g. NSA exploits are developed in the airgap and copied to an attack staging server o

Wouldn't be so sure. Data is eventually copied out of the airgapped side, e.g. NSA exploits are developed in the airgap and copied to an attack staging server on the Internet. And there's one-way connectivity into the airgaps via data diodes. So it's possible that a sufficiently advanced malware got through the data diode, infected the airgap side and hitched a ride out over sneakernet.