The U.S. Army is completely sold on the usefulness of UAVs, and is rushing to buy as many of them as possible. Currently, the army mainly uses three models; the Raven, the Shadow 200, and Hunter. The most numerous one if the four pound Raven. By the end of the year, every combat division will have at least 25 Ravens. The Raven only stays in the air for an hour at a time, but with a range of about 15 kilometers and day and night cameras, it is very popular with combat commanders. One man can carry an entire Raven unit (two or three aircraft, a laptop PC with the control software and radio gear). The 1600 pound Hunters, which stay in the air 18 hours at a time are used by divisions and higher headquarters. The 330 pound Shadow 200 is used by brigades, and can stay in the air for six hours at a time. All of these systems are getting a workout in Iraq and Afghanistan, and that experience is being used to build the next generation of UAVs, which will begin to appear in a few years. In the meantime, the current ones are constantly upgraded to make them more capable and reliable. It was something as simple as cheap, reliable and high resolution digital video cameras that made all the difference, as well as effective ways to transmit the video to the aircraft controller, who could see the view on a laptop computer screen. Simple, effective, and combat commanders can't get enough of it. The U.S. Air Force, which has a monopoly on fixed wing aircraft (courtesy of a deal made with the army half a century ago), has not tried to stop the proliferation of army UAVs, even though these unmanned aircraft are doing work that, for years, air force aircraft did (or, as the army sees it, increasingly doesn't do.)