The army lost track of the $1.5 million drone during a routine training exercise from Fort Huachuca in southern Arizona on Jan. 31, according to a report this week by military publication Stars and Stripes. A hiker found the aircraft 10 days later near Evergreen, Colo., broken in a tree.

The drone, a AAI RQ-7 Shadow, normally has a range of 77 miles. But it was somehow able to stay aloft for its 600-mile trip and at an altitude in excess of 12,000 feet to clear several mountain ranges.

Get Data Sheet, Fortune’s technology newsletter.

Drones that lose their communications with the ground typically hover until a new network link is established and personnel can get the aircraft to return home, according to Stars and Stripes. The army did not say what exactly happened, but the newspaper speculated that the drone’s emergency system failed.

For more about drones, watch:

Fortune contacted the Army, and will update this story if it responds.