According to this article, it's far worse than that: eight inch floppy disks! Capacity might be as much as 1.2MB per disk, but probably less. https://simpleflying.com/americas-atc-floppy-disks-12-billio...
Aha so that answers my question about why they haven't at least switched to USB thumb drives for their sneakernet. These aren't PCs. Probably minicomputers such as a TI-990 or similar. They don't have USB ports.
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If anyone wants to see the guts of an 8-inch drive and how complex it is check out this video from Adrian's Digital Basement.