The battery-powered 'Nano Hummingbird' is the result of a five year effort by AeroVironment Inc, the California-based developer of unmanned aircraft systems.
The Pentagon awarded about four million dollars to AeroVironment to develop the technology.

The miniaturised strong, industry expert said is a step towards technology that could produce drones capable of flying through open windows or sitting on powerlines, capturing audio and video while enemies would be none the wiser. Equipped with a camera, the drone can fly at speeds of up to 11 miles per hour. It can climb and descend vertically, fly sideways, forward and backward, as well as rotate clockwise and counter-clockwise by remote control for about eight minutes.

The 'hummingbird' has a wingspan of 6.5 inches and weighs 19 grams - less than an AA battery. It uses only its flapping wings for propulsion and control. Slightly larger than the average hummingbird, the drone contains motors and other communications systems.

The tiny camera installed in the machine can be used to spy on enemy positions in war zones without arousing detection. AeroVironment's manager on the project Matt Keennon called the 'hummingbird' "a technical challenge" since it "pushes the limitations of aerodynamics."

The success of the programme "paves the way for a new generation of aircraft with the agility and appearance of small birds," Todd Hylton, Hummingbird programme manager for the Pentagon's research arm, said in a statement.

The robotic device was built for the Pentagon's research arm Defense Advanced Research Projects Agency (DARPA) as part of a series of experiments in nanotechnology. The Pentagon had issued seven specific guidelines for the Hummingbird, including that it should be able to hover in a 5-mph wind gust and fly from outdoors to indoors and back outdoors through a normal-size doorway.

While the Nano Hummingbird is a prototype for now, the company would be refining its technology so that it can carry out detailed reconnaissance missions in the future.
The Hummingbird would be a major departure from the current drones that resemble traditional aircraft.