Over the years there have been numerous reports of huge, black, triangular objects, referred to as Big Black Deltas (BBDs), in the night skies above the United States. Some accounts estimate their size to be as much as 600 feet long by 300 feet wide, with a height of 40 feet. A study by the National Institute of Discovery Science (NIDS) hypothesizes that BBDs could be lighter-than-air, blimp-like military vehicles.
To prove their point about the possible origins of BBDs, NIDS researchers plotted the sighting locations on maps of the United States and superimposed the locations of certain military facilities. They discovered a very strong correlation and concluded that "the United States Air Force has been flying large triangular or deltoid shaped aircraft between [its] bases."