An MD-10 cargo jet equipped with an anti-missile system designed to eventually protect passenger aircraft from a terrorist attack took off from Los Angeles International Airport on a commercial flight Tuesday.

The system's designer, Northrop Grumman Corp., said the FedEx flight marked the start of operational testing and evaluation of the laser system designed to defend against shoulder-fired anti-aircraft missiles during takeoffs and landings.

Adapted from military technology, Guardian is designed to detect a missile launch and then direct a laser to the seeker system on the head of the missile and disrupt its guidance signals. The laser is not visible and is eye-safe, the company said.

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"For the first time, we will be able to collect valuable logistics data while operating Guardian on aircraft in routine commercial service," said Robert L. DelBoca, vice president and general manager of Northrop Grumman's Defensive Systems Division.

During the current test phase, which concludes in March 2008, nine MD-10s equipped with the Guardian system will be in commercial service. Katie Lamb-Heinz of Northrop Grumman Electronic Systems said all those aircraft will be freighters. The ultimate goal is to defend passenger airliners.

The testing is part of the U.S. Department of Homeland Security's Counter-Man Portable Air Defense Systems program. BAE Systems has also been working for the government on an airliner defense system.

No passenger plane has ever been downed by a shoulder-fired missile outside of a combat zone. But terrorists linked with Al Qaeda are believed to have fired two SA-7 missiles that narrowly missed an Israeli passenger jet after it took off from Mombasa, Kenya, in November 2002.

The first commercial flight with the Guardian system followed 16 months of tests on an MD-11, an MD-10 and a Boeing 747 using simulated launches of shoulder-fired missiles.