i would guess its something not good like they are sniffing for a serious threat and not divulging their purpose because of the panic that would ensue....so like a suitcase nuke at worst. so sniffing for radiological or getting down low to grabv any kind of signal intel. or its really ayyys and this is more modern analog of the 1896 airship mystery where the phenomenon uses high strangeness and mimicry as some kind of duck blind
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