The vote of confidence came from Under Secretary of Defense Edward "Pete" Aldridge, a one-time skeptic who said he came "pretty close" to killing the program after a pair of crashes claimed the lives of 23 Marines.

"When I looked at the airplane, it was clear we did not have a clue as to how this airplane flew," Aldridge told reporters on his last day as the Pentagon acquisitions and technology chief.

But in a memorandum to the Pentagon's Defense Acquisition Board Friday, Aldridge said that the aircraft, which takes off and lands like a helicopter but flies like a plane, had performed well in a comprehensive flight test program.

"The V-22 is satisfying the threshold levels for all of its key performance parameters," Aldridge wrote.

The Marines have been buying the aircraft at a rate of 11 a year, the minimum to keep production lines open while the fate of the program was being decided.

Aldridge said how fast to ramp up production will be worked out in the 2005 defense budget, but he anticipated a modest initial increase to about 14 a year.

The Marines have wanted to buy 350 of the aircraft to replace their fleet of ageing CH-47 helicopters, and the US Special Operations Command also is expected to order the aircraft.

Despite his initial misgivings, Aldridge said he decided to give the V-22 a second chance because if it worked, it could fly faster and farther than a helicopter and give the US military a new capability.

Of particular concern, however, was the aircraft's vulnerability to a phenomenon known as vortex ring state, in which a rapid rate of descent by the aircraft causes a loss of lift and its engine to stall.

An MV-22 Osprey crash in Arizona that killed 19 Marines in April, 2000 occurred when the pilot bringing the aircraft down too rapidly, causing one of its engines to stall and the aircraft to roll out of control.

In tests, however, the aircraft showed it was capable of very high rates of descent at slow forward speeds, Aldridge said.

The tests determined the aircraft's flight boundaries. A verbal and visual warning system was added to the aircraft to alert the pilot when he or she is close to a vortex ring state condition.

Aldridge's memo said the aircraft has demonstrated "safe and reliable operations in the flight envelope, avoiding vortex ring state conditions."

The testing also showed that the aircraft "can accelerate out of the landing zone faster than any helicopter can," he said. The memo said it showed "combat maneuverability superior to helicopters."

It demonstrated "acceptable handling qualities in low speed flight with crosswinds," showed it could operate on ships safely and is now being to be tested in harsh environmental conditions to determine whether its powerful rotors will kick up too much dust and dirt, Aldridge said.

"We know more about this airplane than ever before," Aldridge said. "There are things we did not know about this airplane up until this flight test program started."

WAR.WIRE