"This machine will change the face of warfare," said Gen. Doug Pearson, commander of the Air Force Flight Test Center at Edwards Air Force Base. "We can do things literally at the speed of light."

The Airborne Laser is a weapons system under development that uses a high-energy laser to destroy a ballistic missile while it is still in the boost phase, shortly after launch.

The laser and its various targeting systems will be mounted aboard the modified Boeing 747 freighter, dubbed the YAL-1A.

The highly modified Boeing 747 -- complete with a shiny new paint job -- landed before a crowd of base dignitaries, project members, family and friends on a clear, cold afternoon, as other members of the bases' family of advanced aircraft roared in the background.

"This airplane is going to be a big deal sometime in the future," said Lt. Col. Keesey Miller, director of the ABL Integrated Test Force. "She's big, she's beautiful, she looks great."

The ABL system, the nation's first directed-energy weapons system, will "transform the future of warfare," he said.

"This is actually just a continuation of many of the exciting things that take place at Edwards," Pearson said. "We've been doing this since the X-1 É and we'll do our best on the YAL-1A."

In creating the YAL-1A, the 747 underwent the most extensive modifications ever performed on such an aircraft. The work was completed at Boeing's facility in Wichita, Kan., where it was flight-tested before coming to Edwards.

The nose of the airliner was removed, replaced with a mock-up of the movable turret used to direct the laser beam at its intended target. Other modifications include a titanium-reinforced underbelly on the fuselage to accommodate the laser exhaust and a reinforced bulkhead inside to protect the crew from the laser equipment.

The aircraft, now based at Edwards, will undergo further preparations for installation of the laser system.

"The next flight of the YAL-1A will be bearing our nation's most powerful laser into the air," said Col. Ellen Pawlikowski, Airborne Laser program director.

The Airborne Laser system targets a missile when it is in the vulnerable boost phase, just after it is fired. At this time, the missile carries a nearly full load of fuel in a pressurized, thin-walled tank. The high-energy laser beams its energy at this tank, causing it to rupture. In this way, the laser uses the missile's own fuel and pressure to bring it down.

"The missile blows itself up," said Maj. Jim Rothenflue, director of engineering for the ABL program at Edwards.

The laser that actually does the damage to a missile is called a chemical oxygen iodine laser, or COIL. It is created by mixing chemicals in the right proportions and conditions to create a high-energy beam of light.

The Airborne Laser is really a system of four lasers. Three electronic lasers are used for targeting purposes, and the fourth is the destructive COIL.

The beam -- about the size of a basketball where it hits the target -- has a range of "hundreds of kilometers," Rothenflue said; the actual number is classified.

In order to test the laser system before installing it in the modified 747, a test laboratory was built on the ground at Edwards. This laboratory is housed in an unusual-looking building at the South Base site that once housed the B-2 program.

Built around a 747 fuselage, the Systems Integration Laboratory -- or SIL -- looks like a 747 flew into a too-small shed and got stuck, its nose and tail sticking outside.

"We can make all our mistakes here," Rothenflue said. "There's a lot of risk reduction going on here."

For the ground tests, the laser will be fired into a range simulator, essentially a large "photon catcher," which captures the laser beam and transfers the heat energy to a mass of copper.

The first test firing of the COIL on the ground is expected in the late spring or early summer of next year. The ground tests are planned for about two months before the system is transferred to the aircraft.

Besides providing the facility for testing the laser's operation, the SIL is also useful for testing how the system will fit inside the 747 aircraft.

"That's what's great about using the fuselage," Rothenflue said.

The ABL is quickly becoming one of the biggest programs at the base, with more than 200 people -- military and contractor personnel -- already involved. That number could double before the program is finished, Rothenflue said.

The first operational test of the entire ABL system is planned for December 2004, when it will be used against a SCUD missile.

Although test firing of the laser will occur elsewhere, all flights will take off and land at Edwards.

The program actually had its beginnings 30 years ago at Kirtland AFB, N.M., where it is still headquartered. The first attempt at such a weapon, mounted on a Boeing 707 aircraft, intercepted five air-to-air missiles.

Interest in such a weapon system was reignited during the Gulf War, when SCUD missiles were a threat to allied forces.

In addition to the Air Force, private-sector contractors working on the ABL are The Boeing Co., TRW Space and Electronics Group and Lockheed Martin Missiles and Space.

Although it began as an Air Force program, the ABL is now part of the Missile Defense Agency, the umbrella organization coordinating all of the nation's missile defense efforts.