The X-47B marks a paradigm shift in warfare, one that is likely to have far-reaching consequences. With the drone’s ability to be flown autonomously by onboard computers, it could usher in an era when death and destruction can be dealt by machines operating semi-independently.

Although humans would program an autonomous drone’s flight plan and could override its decisions, the prospect of heavily armed aircraft screaming through the skies without direct human control is unnerving to many.

“Lethal actions should have a clear chain of accountability,” said Noel Sharkey, a computer scientist and robotics expert. “This is difficult with a robot weapon. The robot cannot be held accountable. So is it the commander who used it? The politician who authorized it? The military’s acquisition process? The manufacturer, for faulty equipment?”