ASHINGTON, Jan. 16 — Richard Reid, who was overpowered on a Paris-to-Miami flight last month as he tried to light explosives in his shoes, was a Qaeda-trained terrorist who tried to bring down an airliner carrying nearly 200 people, according to a federal grand jury indictment filed in Boston today.

The nine-count indictment, which includes charges of attempted murder and attempted use of a weapon of mass destruction, said Mr. Reid, a 28-year-old British citizen, was trained at "various times" in Afghanistan. The indictment provided no other details about Mr. Reid's ties to Osama bin Laden's Qaeda network but made it clear that prosecutors regarded him as a terrorist.

Mr. Reid is being held without bail in Plymouth, Mass., and he will be tried in federal court in Boston. He faces a maximum sentence of life in prison if convicted. None of the offenses he is accused of are punishable by the death penalty.

At a news conference today, Attorney General John Ashcroft credited several passengers and crew members aboard Flight 63 with preventing Mr. Reid from detonating the explosives hidden in his sneakers.

"But for the vigilance of the flight crew and the courage of the passengers on Flight 63, Richard Reid may have succeeded in what today's indictment charges was his ultimate goal: the destruction of Flight 63 and the 197 people on board," Mr. Ashcroft said.

Law enforcement officials said they were still investigating how deeply Al Qaeda was involved in Mr. Reid's plan. But Mr. Ashcroft made it clear that he believed that Al Qaeda was fully responsible for the attempted shoe bombing and represented a significant threat in the United States.

"Reid's indictment alerts us to a clear, unmistakable threat that Al Qaeda could attack the United States again," Mr. Ashcroft said. "We must be prepared, we must be alert, we must be vigilant. Al Qaeda-trained terrorists may act on their own, or as part of the terrorist network, but we must assume that they will act."

Mr. Ashcroft suggested that the Reid case, with the intervention of passengers on the plane, justified his insistence on issuing terror warnings, even when the threats were vague and offered little guidance about how people could respond.

The F.B.I. has issued three such alerts since Sept. 11, with the current warning due to expire in March, after the Winter Olympics in Salt Lake City.

In Mr. Reid's case, Mr. Ashcroft said, "Our trust in the common sense of people who act in the face of terrorism was vindicated."

One of the charges against Mr. Reid accused him of the attempted wrecking of a mass transportation vehicle, a new criminal violation that was one of the measures enacted by Congress after the Sept. 11 attacks. That charge and three others against Mr. Reid carry a maximum sentence of life in prison.

Mr. Reid was also charged with the attempted use of a weapon of mass destruction and attempted murder. In addition, he was accused of placing an explosive device on an aircraft, interfering with a flight crew, attempted destruction of an aircraft and using a destructive device during a crime of violence.

American Airlines Flight 63 was over the Atlantic en route to Miami on Dec. 22 when Mr. Reid tried to ignite a fuse hanging from one of his shoes. Several passengers and crew members wrestled with Mr. Reid, pinning him down, with one passenger brandishing a fire extinguisher, until a physician on board administered a sedative.

The flight was diverted to Boston where a federal magistrate ordered Mr. Reid held without bail. Federal prosecutors initially charged him with the attempted bombing in a criminal complaint that was superseded by today's indictment.

The charges against Mr. Reid came one day after federal prosecutors in Virginia charged John Walker, an American captured as a Taliban fighter in Afghanistan, with conspiring to kill United States citizens and supporting a terrorist group.

An F.B.I. official said last month in a court hearing in Boston that forensic experts had determined that the plastic explosives in Mr. Reid's shoes could have blown a hole in the aircraft's fuselage and destroyed the jetliner if he had detonated the bomb against the airliner's hull.

Mr. Reid's recent past remains a mystery. His movements in recent months closely resembled those of a Qaeda operative known as "Abdul Ra'uff," whose travels as a terrorist scout were described in an article published today by The Wall Street Journal.

The Journal article said that Mr. Ra'uff traveled to Israel on a British passport scouting possible terrorist targets. He also visited Egypt, Pakistan and Turkey, travels that were much like Mr. Reid's.

The newspaper's report was based on material found on one of two computer hard drives that its reporters purchased for $1,100 in Afghanistan. The newspaper said that the computers were taken by a looter in mid-November from an office that had been used by Al Qaeda in Kabul.

Today, Justice Department officials said that Mr. Ra'uff and Mr. Reid could be the same person. One official said that The Wall Street Journal had provided a copy of the computer material to investigators.

Investigators have been trying to determine whether Mr. Reid was operating as part of a Qaeda plan and if the organization took part in the attempted bombing, possibly by helping him construct the explosive device. But so far, authorities said, investigators have not determined whether others helped Mr. Reid.

Mr. Reid attended the same mosque in London as Zacarias Moussaoui, a French citizen of Moroccan descent, who so far has been the only person charged in the United States with complicity in Sept. 11 attacks. Law enforcement officials have said that they do not know whether Mr. Reid knew Mr. Moussaoui, who is awaiting trial in Alexandria, Va.