Theories persist about mystery drones seen in rural region

People insist they have spotted fleets of large drones crisscrossing rural America's night sky, their mission mysterious, raising questions that have veered into conspiracy theories and launching an investigation.

Authorities in Colorado have tried to put those theories to rest, announcing that they have confirmed nothing unusual or criminal about dozens of weird drone reports since November. They were mostly hobbyist drones, commercial aircraft, stars, planets and weather phenomena.

Yet if history is any guide, the investigation that used a heat-detecting plane in Colorado's mystery-drone highway, with sightings that stretched into Nebraska and Wyoming, will settle nothing for many people.

Speculation persists about drones said to be as big as cars, flying in groups in grid patterns at night.

"Even if the military has plausible deniability with this, defence contractors might be involved," Dan Carlson, a drone-spotting retired meteorologist in western Nebraska, said Tuesday. "By the time they confess up to it, they'll have been in sky for four years."