One that springs to mind is the aerial mine concept. Has this type of mine ever been developed?
Just to be clear, you're talking about devices such as a floating type of mine, not land/naval mines that are deployed by aircraft, right? If so than I don't think there was ever such a thing. During WWII the US and British navies used barrage balloons to scare away most of the low-flying enemy fighters. I guess those sort of acted as aerial mines.
i know of some mines that are deployed by are but are not floating mines, they are deployed by french tornados from a drop pod which also carries mines which propel themselves into the ground and when anything gets close, and BOOM there goes the dynamite
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