LOS ANGELES - An MD-10 cargo jet equipped with Northrop Grumman's Guardian antimissile system took off from Los Angeles International Airport on a commercial flight yesterday, the company said.

The FedEx flight marked the start of operational testing and evaluation of the laser system designed to defend against shoulder-fired antiaircraft 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.

"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 is scheduled to conclude 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 would be freighters. The ultimate goal is to defend passenger airliners.