I've always been more interested in Semi-Bouyant Reconaisance Drones (SBRD) which are 20 Foot diameter hard shelled gas filled saucer shaped airships. The British Army use them, always at night, and they make up 100% of all the UFO sightings over Salisbury Plain.
The Rendlesham UFO incident in the 1980's was actually one of these machines. I've had a few beers with one of the insturctors and they sound fun to fly. These are totally remotely operated vehicles and have been in develpment since the 1960's. The early ones were cigar shaped but this shape caught side winds and affected maneuverability, so they changed to a suacer design on the 1970's and stuck with that.
Aparently, the instructor told me, when they see a bunch of UFO spotters up on a hill thtough the infared camera view, they turn on the landing lights and perform little aerobatics displays, carve circles into the crops in fileds, etc. The Army had a bit of a clamp down on these shenaigans after the media suddenly became interested in crop circles and tales of UFO visits in the area. These are supposed to be top secret machines after all.
I'd like to build one someday, OK a scaled down version. Just think of the mischief one could have creating fake UFO sightings at night, etc.