The FBI confirmed Monday that the explosives in the shoe of a man who had to be subdued on a Saturday flight bound to Miami from Paris were powerful enough to have caused a "major disaster."

Richard C. Reid was arraigned Monday and will remain in prison for a few days more at least. Authorities say they have no evidence he is connected to Usama bin Laden or the Sept. 11 terrorist attacks.

Dressed in an orange jail jumpsuit and sandals, his long, brown hair covering part of his face, Reid sat alone in front of U.S. Magistrate Judge Judith Dein and responded with a curt "Yeah" when she asked if he understood the charge against him.

Reid, 28, is charged with intimidation or assault of a flight crew causing interference with their duties. He asked for a court-appointed attorney to represent him at trial.

The FBI confirmed following the arraignment that the explosives in Reid's shoe were functional and, if detonated, could have been devastating.

"It would have resulted in significant damage and we did avert a major disaster," said Charles Prouty, the Special Agent in Charge of the Boston FBI office. He declined to detail what the explosives were.

Reid was ordered held in federal custody until a bail hearing Friday, and faces a maximum of 20 years in prison if convicted. The FBI said more charges are likely.

A U.S. government official speaking on condition of anonymity said there was no evidence that the suspect was connected to bin Laden or the Al Qaeda terrorist network.

Reid tried to destroy an American Airlines flight from Paris to Miami Saturday when he tried to light a shoe full of plastic explosive with a match, authorities said. Quick-eyed flight attendants and half a dozen other passengers worked together to stop and restrain Reid. Two doctors onboard used the plane's medical kits to sedate him.

But it's still not clear exactly who Reid is . . . or if he is Reid at all. The hulking suspect was listed in court papers Sunday as Richard C. Reid from the name on his British passport, and officials at Scotland Yard said they believed he was a British national. But French authorities identified him as a Sri Lankan named Tariq Raja. They said he also has gone by a third name, Abdel Rahim  Adding to the confusion, a French official said Monday that investigators in France consider him to be a British national.

No matter who he is or whom he knows, airports around the country and in Europe ratcheted up security yet another notch after the midair scare, requiring passengers to send their shoes through X-ray machines before boarding.

The Federal Aviation Administration on Sunday ordered U.S. airlines and airports to be more vigilant in screening passengers' shoes. The order follows a similar one issued Dec. 11 warning that hijackers might try to smuggle weapons in their footwear.

That poses a problem for American airports. In the United States, the current generation of walk-through machines that screen passengers for weapons can't detect plastic explosives, and most airline passengers and their carry-on bags aren't checked for explosives by other means, such as bomb-sniffing dogs.

While U.S. airlines have a congressionally mandated deadline of Jan. 18 for having a system in place to inspect all checked baggage for explosives, walk-through devices that could detect them on passengers are still in the development stage.

"It's a hole that needs to be looked at," said Capt. John Cox, executive air safety chairman of the Air Line Pilots Association.

Airline experts say the only way to prevent a passenger from bringing an explosive on board is to single out potential terrorists through computerized profiles and then to call in bomb-sniffing dogs or conduct body and clothing searches.

"Profiling is the key," said David Stempler, president of the Air Travelers Association, an advocacy group. "Security is composed of two parts. The first is who are you and the second is what are you carrying."

It took humans to sniff out Reid and his potentially deadly high-top basketball sneaker.

Passengers said they noticed the 6' 4", ponytailed man standing alone and stone-faced before boarding.

"He had a blank look," Nicholas Green, 27, said. "The people who had seen him remembered him."

During the flight, the suspect, who was sitting behind the wing in the coach section, lit a match, but he put it in his mouth when confronted by flight attendant Hermis Moutardier, according to an FBI affidavit.

She told the captain and returned to see Reid with a match held to the tongue of his sneaker, then noticed a wire protruding from the shoe. She tried to grab the sneaker, but Reid allegedly pushed her to the floor, and she screamed for help.

Another flight attendant, Cristina Jones, intervened and the 6-foot-4 Reid bit her, authorities said.

"He bit Ms. Jones on the thumb and Ms. Moutardier threw water in his face," FBI agent Margaret G. Cronin said in the statement.

That's when passengers reached Reid and subdued him.

Marcos Obermaier, 42, of Miami, a passenger who guarded Reid with a fire extinguisher, told ABC's Good Morning America that a group jumped Reid immediately.

"He definitely had a crazed look in his eyes," he said.

Kwame James, a Trinidadian who plays professional basketball in France, helped subdue the man. He said that when other passengers asked Reid why he did it, "He just kind of smiled and didn't say too much."

When one passenger asked about his motivation, Reid responded, "Don't worry. You'll see," James said.

The plane, carrying 183 passengers and 14 crew members, was escorted to Logan Airport by two F-15 fighter jets.

French police are probing how Reid eluded increased security measures at Charles de Gaulle airport outside Paris, where Flight 63 originated.

French authorities said Reid had tried to board the same flight a day earlier but was turned away after raising suspicions. They said the suspect was given permission to board after intensive questioning, but by then had missed Friday's flight. He had only one small bag with him and said he was traveling to Antigua to visit relatives, police said.

The Associated Press contributed to this report.