Sentient.

This is coolbert:

Please believe me this is not Skynet. The military drone did not become sentient. Merely communications was lost between the drone and the operator station on the ground. 

"Latvian drone wrests control from human overlords and shuts down entire nation's skies"

"Please phone us if you see our missing 26kg [about fifty pounds] aircraft, say authorities"

Article by Gareth Corfield Mon 4 May 2020.

"Latvia’s skies have been closed to long distance flights because a military-grade drone is 'uncontrolled and lost' somewhere above the eastern European nation – and nobody knows where it has gone."

"Local news website Apollo reported over the weekend that a test flight went disastrously wrong when a Latvian drone firm lost control of one of their remote-controlled aircraft."

That concept of sentience complex [?] but generally defined as self-awareness with an ability to think for itself. A sentient drone [as controlled by onboard computer with AI programming] controlled by a ground station human operator perhaps according to science-fiction authors no longer obeying commands, operating in an uncontrolled manner. See here a discussion of how to determine if a computer [as might be found on a military drone] becomes sentient.

This particular UAV able to fly for ninety hours until power source is exhausted and the machine crashes to earth. Presumably this is what occurred. 

Skynet a way off but maybe not so long off!

coolbert.