A prototype of a supersonic airplane crashed spectacularly Sunday immediately after the rocket that was carrying it was launched in Australia's Outback, officials from the National Aerospace Laboratory of Japan said.

It was to be the first test flight of the prototype but instead became the latest in a string of aerospace failures for Japan.

The rocket was supposed to carry the unmanned, 11.5-meter-long prototype to an altitude of about 20 km and then detach, having accelerated the plane to Mach 2.

The scaled-down engine-less jet, controlled from the ground at the launch site in Woomera, South Australia, was to fly for about 12 minutes before being slowed by a parachute and brought back down to Earth.

"The plane and the rocket must have failed to separate," a laboratory official said.

The rocket tipped to the left and fell after about 10 seconds. The cause of the crash has yet to be determined, the official said.

The experiment was part of a supersonic transport project that began in 1995. It aims to develop an advanced transport aircraft that can travel at twice the speed of a conventional passenger jet but produce less noise and emit less nitrogen oxide.

The National Aerospace Laboratory transported two experimental planes to Australia and planned to conduct four test flights before 2003.

The first test was originally scheduled for Thursday but was delayed due to strong winds.

Also recently in Woomera, an experimental rocket crashed after its guidance fins moved during flight and sent it off course following its launch.