It was considered a stunning turn in warfare when a remotely controlled aircraft on a reconnaissance flight over Afghanistan spotted a Taliban convoy and fired a jury-rigged Hellfire missile, striking and destroying the target.
The headline-grabbing flight in late 2001 -- though rudimentary and under remote human control -- marked the first search-and-destroy mission by a flying drone, and it propelled robotic warfare from the pages of science fiction to the battlefield.
Now, behind a barb-wired fence and double security doors in Palmdale, Northrop Grumman Corp. engineers are building what could become the ultimate flying robot: a jet fighter controlled by a computer. It would take off from an aircraft carrier, drop a bomb on an enemy target and then land back on the carrier, all autonomously.
The first carrier test flight of the X-47B -- including a shipboard take-off and landing -- is slated for late 2011. If successful, the flight could redefine naval aviation, analysts said.
"If you were to think of major milestones in aviation history, it will be on the shortlist," said John Pike, director of GlobalSecurity.org, a defense and space policy research website.
The Pentagon and the U.S. intelligence agencies have long used flying drones to survey a battlefield or spy on the enemy. They are typically equipped with powerful cameras and are controlled remotely by humans much like hobbyists flying model aircraft, though the military versions are controlled from far-greater distances.
But no aircraft, besides those in science fiction movies, have been able to carry out a combat mission controlled entirely by a computer.
Moreover, landing on an aircraft carrier plying the ocean at 30 knots (or 34.5 mph) and pitching with the waves is considered an extremely difficult feat for even the most seasoned pilot.
"The performance of the aircraft isn't an issue anymore," said David Ochmanek, Rand Corp. senior defense analyst of unmanned planes. "The sole remaining issue that hasn't been addressed -- because it is so difficult -- is landing them and having them take off."
The Navy, with its checkered experience with remotely controlled aircraft, has taken a cautious approach to the development of the X-47B.
In the 1960s, the Navy tried unmanned helicopters developed to hunt Russian nuclear submarines.
These drones were controlled from ships. But the Navy lost half of them, mainly because of problems with the electronic equipment that controlled the copters. The program eventually was scrapped.
If the X-47B can demonstrate reliability in taking off and landing on carriers during the 2011 sea trials, "it would have significant repercussions for naval operations," Pike said.
The aircraft would be able to fly farther and stay aloft longer than piloted planes, which are limited by human endurance.
It would also allow a $4-billion aircraft carrier with a crew of 5,000 to stay farther from harm's way.
In Iraq and Afghanistan, Navy fighter pilots have had to fly longer missions lasting as many as 10 hours, or about as long as the pilot's body can endure without faltering.
Unmanned planes would be able to fly missions lasting 50 hours or longer, limited only by fuel capacity.
Moreover, the planes would be able to fly the most dangerous missions, such as first strikes to destroy radar installations and antiaircraft missiles in enemy territory, paving the way for piloted fighters and bombers to strike less-dangerous targets.
Winning the $635.8-million contract to develop the X-47B last August was important for Northrop Grumman, said Loren Thompson, a military policy analyst for the Lexington Institute.
It validated the Century City-based defense contractor's "major long-term bet on unmanned aircraft," Thompson said. "They believe it is the wave of the future."
The company, better known for building the B-2 stealth bomber, has been pushing hard to develop the nation's most advanced robotic aircraft.
In the last decade, Northrop has invested hundreds of millions of dollars in developing unmanned planes, including spending $140 million in 1999 to acquire a small San Diego firm that was building the high altitude Global Hawk spy plane.
Northrop, the nation's third-largest defense contractor, also builds military ships and is one of the largest federal information technology contractors. It has about 27,000 workers in Southern California.
Unlike drones that are controlled remotely by humans, Northrop aircraft such as the Global Hawk fly under the control of an onboard computer. The plane's mission is preprogrammed into the computer so it takes off, completes its flight and then lands, all autonomously. Humans still monitor the mission and have the ability to alter the craft's flight path or destroy it if it goes off course.
Still, the plane is likely to raise several thorny legal questions as it nears the possibility of carrying out combat missions later next decade, including the liability of killing noncombatants because of a programming error or a computer glitch.
The X-47B is being modeled after the Global Hawk in the way it is controlled, though the X-47B's slick, kite-like shape appears more menacing than the spy plane with its plank-like wings, which are designed to let it fly at very high altitudes at low speeds.
The six-year Navy contract calls for Northrop to build two X-47Bs that would be used to demonstrate the ability of pilotless planes to fly off of aircraft carriers.
If successful, the Navy plans to develop a combat version of the aircraft in 2013 with the goal of having an operational unit by 2020.
The Navy also is looking at multiple roles for the plane including reconnaissance and anti-submarine missions.
Analysts said the Navy could buy 150 to 200 aircraft, a contract potentially worth tens of billions of dollars.
About 200 engineers and technicians are working on the program in Southern California at Northrop Grumman facilities in El Segundo, Rancho Bernardo and Palmdale, where the planes will be assembled.
The workforce is expected to grow to about 400 as the program expands.
Many of the engineers are familiar with carrier operations, having helped develop such Navy carrier aircraft as the F/A-18 Super Hornet.
The first test flights of the X-47B are expected to be conducted at a military airfield in early 2009 before it begins sea trials in 2011.
Scott Winship, the X-47B program director for Northrop, believes the plane will be able to land on a carrier with more precision than a human-piloted plane.
Numerous sensors on the plane can gauge its distance and position while landing with far more accuracy than a pilot's eyeball. At the same time, the computer can make adjustments far faster.
In computer simulations, the X-47B, using algorithms developed for the aircraft, was able to land successfully 8,000 times, never missing a landing point by more than 9 inches, Winship said, adding, "If we're successful, it's going to change the way Navy operates."