Boeing’s X-45 Unmanned Combat Air Vehicle (UCAV) is the first of its type — a fighter plane without a pilot. Military experts say UCAVs will play a key role in future warfare, because they are smaller, lighter, cheaper, and more agile than piloted aircraft. Unmanned combat planes are envisioned as a “first day of the war” strike force capable of attacking enemy air defenses without risking pilots’ lives. Boeing’s UCAV, sponsored by DARPA and the Air Force, underwent ground tests this year and may have begun flight tests by the time you read this. A Navy UCAV designed by Northrop Grumman will soon follow. UCAVs could enter service as early as 2010.