US Special Forces are testing PD-100 Black Hornet drones, one of a new breed of small drones which can autonomously fly in many different environments and, experts warn, present scientific, technical and ethical challenges for military and civilian applications.

The Black Hornet drone weighs 18 grams and carries a regular or thermal camera; it has a maximum flight time of around 25 minutes, a top speed of 10 m/s and a range of more than 1.5 km. Its camera relays video and still images to a handheld control terminal.