Despite the crashes, military officials remain bullish on unmanned air vehicles, or UAVs. The high-profile role of planes like Northrop Grumman's Global Hawk and the General Atomics Aeronautical Systems Predator has helped attract interest in the technology, military officials and analysts said.

"I doubt you could have found 12 congressmen prior to Sept. 11 who could have told you what a Predator was, much less who made it," said Larry Dickerson, senior unmanned air vehicle analyst for Forecast International/DMS in Newtown, Conn.

Dickerson predicts the global market for military drones could be worth $7.5 billion over the next decade.

The Defense Advanced Research Project Agency, which develops future technologies for use by the Pentagon, has at least a half-dozen other UAVs and UCAVs — the "C" stands for combat — under development. Among them are jet- and rotor-driven craft, some no larger than a cake pan.

On Thursday, it displayed one of the larger of the planes, the X-45.

Developed by DARPA, the Air Force and The Boeing Co. for $256 million, the sleek, tailless jet is the first unpiloted plane to be developed specifically to carry weapons into combat. Beginning in Vietnam, other drones, including the Predator now flying in Afghanistan, have been modified to carry missiles.

"This is designed as a tactical aircraft. Global Hawk and Predator were not," said Col. Michael Leahy Jr., manager of DARPA's UCAV program.

Boeing has built two X-45s so far, one trimmed in blue, the other in red. Only the blue plane has flown, on May 22 and June 13 above the Mojave Desert. The second will begin flight tests this fall.

The two Y-shaped planes both sport a gaping air intake instead of a canopy. The planes have a 34-foot wingspan and are just 4 feet thick, giving them a slim, stealthy profile.

Those working on the X-45 call it the "Stingray." Leahy said he prefers the nickname "Shrike" for what could eventually be designated the A-45.

Military officials said the slightly larger production model of the plane will be able to carry more than 3,000 pounds of bombs to drop on enemy radar and missile batteries, perhaps by 2010.

The use of drones in combat in Afghanistan has already become the stuff of pop culture. This week's "Doonesbury" cartoon strip is a running gag about a government agent's intern accidentally launching a Predator and firing a missile.

Richard Aboulafia, director of aviation for the Fairfax, Va.-based Teal Group, said it's premature to spell out a combat role for robot planes when their use for less risky reconnaissance missions has yet to be perfected.

He said, "We're getting way ahead of ourselves here."