On February 23rd, the U.S. Navy's X-47A UCAV (unmanned combat aircraft) made it's first flight. Development of this aircraft began in 2001. The Air Force is also testing the X-45 UCAV, which also has a naval version (the X-46). The X-45 program began in 1999, and the 16,000 pound (max take off weight, with 4,000 pounds payload) aircraft is expected to be ready for operational tests in 2006. The X-46 has a different wing layout, and a range of 1100 kilometers, carrying a payload of 4,000 pounds. The X-47 also has a 4,000 pound payload and a range of 1,600 kilometers. Unlike the X-45, which is built to be stored for long periods, the X-47 is built for sustained use aboard a carrier. All of these aircraft are very stealthy and can operate completely on their own (including landing and takeoff, under software control). The UCAVs would be used for dangerous missions, like destroying enemy air defenses, and reconnaissance.