<Large black blimps have about a zero percent usefulness to the military.

The cost versus the loss ratio of these things in a combat zone would be astronomical.



Actually, if you go on the admittedly unproven assumption that these are military vehicles, the fact that they seem to be extremely hard to see or detect by most normal means may indicate a lot more usefulness than you might think. What would be really difficult would be hiding them from satellites when they're parked.

Some folks have theorized that these things are able to paint artificial active backgrounds, like starscapes, across their surfaces, making them "invisible" at low altitudes to the casual observer. Sightings of opaque black triangles that suddenly "vanish" could be explained this way. Such a technique might make them hard to see from high altitudes if they were landed as well. Just speculating.

The electrokinetic propulsion bit also has the distinct aromatic farm odor.

I would tend to agree here. Most attempts at electrokinetic propulsion give off electromagnetic noise that in the visual spectrum would be the equivalent of a road flare. Although I'm no expert, I would think a "stealth" electromagnetic propulsion system might be quite difficult to accomplish.

In any case, the "military secret vehicle" theory is a lot more plausible than aliens.