A Boeing 747 jumbo jet equipped with a massive laser gun shot down a Scud-like missile over the Pacific on Thursday night, marking what analysts said was a major milestone in the development of the nation's missile defense system.

The test over a military range near Point Mugu is expected to renew debate over spending billions of dollars for a system that seemed so far behind schedule that the Pentagon decided to significantly curtail its budget last year.

"Proving this technology is game-changing," said Loren Thompson, a military policy analyst for the Lexington Institute, a think tank in Arlington, Va. "The program's funding has been hanging on by a thread."

The airborne laser is designed to defend against ballistic missiles by shooting them down while they are lifting off.

During the test, a 747 took off from Edwards Air Force Base in the Mojave Desert. The laser, which was affixed to the 747 and powered by chemicals loaded into the aircraft, shot a super-heated, basketball-size beam that traveled 670 million miles per hour to incinerate a missile that was moving 4,000 mph, the Pentagon said.

It took just a few seconds for the beam to create a stress fracture in the missile, triggering it to split into pieces. "The revolutionary use of directed energy is very attractive for missile defense, with the potential to attack multiple targets at the speed of light, at a range of hundreds of kilometers and at a low cost per intercept attempt compared to current technologies," the U.S. Missile Defense Agency said.

Since the airborne laser program began in 1996, it has cost the government billions in overruns with little to show for it. Because of the poor track record, Defense Secretary Robert Gates announced cuts in the program in April. And the program was not even in President Obama's 2011 budget. However, the successful demonstration may change all that, Thompson said.