(SOUNDBITE OF MARIUS CONSTANT'S "THE TWILIGHT ZONE THEME")

STEVE INSKEEP, HOST:

Enter another dimension, a dimension not of sight and sound but of drones. A U.S. Army drone was on a training flight over southern Arizona and vanished. A hiker later found it stuck in a tree 600 miles away in Colorado. Nobody knows how the $1.5 million aircraft got there. Apparently, the operator on the ground didn't fly it, which raises the possibility that drones, unmanned aerial vehicles, have begun flying themselves. It's MORNING EDITION. Transcript provided by NPR, Copyright NPR.