WASHINGTON, July 19: A jumbo jet retrofitted to carry a laser gun capable of shooting down enemy missiles has been flight-tested for the first time as part of US efforts to build a national missile defence system, according to defence and industry officials.

The modified Boeing 747-400 took off from an airport in Wichita, Kansas, on Thursday for a two-hour flight to check the aircraft’s aerodynamic performance and system operation, the officials said.

The test marked the beginning of a months-long flight-worthiness test programme for the first airborne laser aircraft, which sports a nose turret and top-mounted laser targeting pod.

The plane is expected to become a key component of the multi-layered missile defense system envisaged by President George W. Bush.

The concept calls for using a high-energy chemical laser aboard the aircraft to shoot down ballistic missiles in their boost phase.

Laser-equipped Boeings would patrol the skies near conflict zones at the altitude of about 12,000 metres, scanning the horizon for the plumes of rising missiles.

A tracking laser would then acquire and follow missiles while computers aboard the plane measure the distance and process other missile flight data.

When the targeting is complete, a laser gun would fire a three- to five-second burst at the missile in an attempt to perforate its surface and bring about a fuel explosion.

“This represents a major step forward for the airborne laser program,” Air Force Colonel Ellen Pawlikowski said in a statement issued after the test.—AFP