T & P
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I can't remember which articles there were (one at least was posted here, I'm sure?), but I think an image is emerging that suggests the Chinese have been exploiting a weakness in US security, whereby the Americans' radars, scanners and other surveillance equipment had been programmed to ignore slow-moving small objects and flag up just traditional fast moving aereal targets. It might be that only after the first, much larger balloon was detected that NORAD decided to tweak the search parameters of their surveillance radars to include such objects, and they are now being picked up.
If so, there's a good chance there have been plenty of previous ones that have floated past the US completely undetected.
If so, there's a good chance there have been plenty of previous ones that have floated past the US completely undetected.