With the nation on heightened terrorist alert, the crash raised immediate anxieties of a fresh assault. It came two months and a day after hijacked aircraft destroyed the World Trade Center and damaged the Pentagon, and coincided with a dense assembly of global leaders at the United Nations. But law enforcement authorities said with unusual speed that they had no indication of criminal involvement. Marion C. Blakey, who chairs the National Transportation Safety Board, said, "All information we have currently is that this is an accident."

The Bush administration reported no prior threats against civil aviation, no unusual communications from the cockpit, and no warning that Flight 587 was in trouble until it crashed. But officials emphasized that it is much too soon to be sure that terrorists or saboteurs had no role in the disaster. "We have not ruled anything in, we have not ruled anything out," said White House spokesman Ari Fleischer.

The doomed flight lifted off at 9:13 a.m., well after its scheduled 8 a.m. departure. Neither American nor the Federal Aviation Administration supplied a reason for the delay. The aircraft banked counterclockwise through a climbing three-quarter turn over Jamaica Bay. Air traffic controllers lost radar and radio contact at 9:17 a.m., four minutes after the plane took to the air.

It fell to earth in the Rockaway section of Queens, a middle-class neighborhood that lost scores of firefighters and financial workers on Sept. 11. Burning jet fuel settled into the sewers, then belched flame and smoke up storm drains to the street.

The National Transportation Safety Board sent a "go team" of nearly 100 investigators from Washington, and Fleischer said at the White House that the safety board would lead the crash probe. The NTSB concentrates on human, mechanical and system failures.

Barry Mawn of the FBI's New York office said from the scene that the bureau, as usual, would open a parallel probe into the crash and designate the wreckage a crime scene. In cases in which there is evidence of foul play, the FBI normally takes the lead investigative role.

Blakey, the safety board's chair, said tonight that investigators had recovered the cockpit voice recorder. Two such "black boxes" -- actually painted orange to make them conspicuous at a crash site -- are housed in the aircraft's tail, one for instrument readings and aircraft movements, and one for cockpit voices. If both boxes are recovered intact, they should provide the entire technical and sound record of the brief flight.

Blakey said wreckage had fallen in three places. One cylindrical piece, resembling an engine housing, fell onto a Texaco station, where it landed six feet from the fuel pumps. Video footage showed a hole the size of a car tire in its exterior. Most of the fuselage cratered into an intersection at Newport Avenue, sending columns of dense black smoke aloft over leaping flames. And Blakey said a wing section plunged into Jamaica Bay. Coast Guard video later showed the vertical fin from the aircraft's tail -- not a wing section -- being fished from the water by crane.

With the cause of the crash uncertain and security fears at a peak, the FAA imposed a ban on takeoffs at all airports within a 25-mile radius of New York at 9:26 a.m. Before noon it confined that restriction to the three principal airports -- JFK, La Guardia and Newark International. By afternoon only outbound flights from JFK were restricted, while the Port Authority checked the jet fuel there for contamination.

Commercial airlines also had new security measures in place. Paul Takemoto, speaking from the Operations Center of the Federal Aviation Administration, told reporters in a conference call that since Sept. 11, all major airlines have completed reinforcements to aircraft cockpit doors intended to prevent entry by would-be hijackers. Authorities declined to discuss whether an armed air marshal had been aboard Flight 587.

President Bush learned of this morning's crash at 9:25, minutes after air controllers lost contact with Flight 587. A military aide passed him a note during an unrelated national security briefing in the White House Situation Room.

Fleischer said the president urged Americans to maintain faith in commercial aviation. "The president continues to believe that people need to travel, people need to get on with their lives," he said.

"The New York people have suffered mightily," Bush said later, appearing briefly with former South African president Nelson Mandela. "They suffer again. But there's no doubt in my mind that New Yorkers are resilient and strong and courageous people and will help their neighbors overcome this recent incident that took place."

The wide-body A300 was built by Airbus Industrie, a European consortium. It was the first aircraft produced by Airbus, and is now out of production. American operates 35 of the Airbus jets, specifically the A300-600 variant. The one lost today was built in Toulouse, France, and entered service with American on July 12, 1988. That corresponds to early middle age for a modern jetliner.

Its last light maintenance check was Sunday, and its last major inspection was Oct. 3.

Two General Electric engines powered the aircraft, each designed to fly 10,000 hours between overhauls. The left engine had logged only 694 hours since its last overhaul, but the right engine had 9,788 hours of flight time and would have been removed for major maintenance soon.

In recent years, the FAA has issued scores of compulsory orders for mechanical adjustment of the A300 or its separately manufactured engines. Known as "airworthiness directives," they specify remedies for potential defects that could jeopardize flight safety. One, in April, described a potential "dual engine surge" during takeoff. Another, in September, ordered modifications to fuel level sensors to prevent overheating and the possibility of an explosion.

Only last month, on Oct. 7, the FAA updated a directive on the General Electric engines -- CF6-80C2 series turbofans -- involved in today's crash. It mandated new inspections "to detect cracks in the bottoms of the dovetail slots that could propagate to failure of the disk and cause an uncontained engine failure."

There was no evidence today whether this or any other known risk played a role in the crash.

Doctors from around the city converged on a triage site set up at P.S. 114, the nearest elementary school, but found little to do. Gilbert G. Makabali, chairman of the department of surgery at St. John's Episcopal Hospital, said there were no survivors from the plane or the neighborhood to treat. Later, 34 people straggled to the Peninsula Hospital Center emergency room with cuts, bruises and smoke irritation to lungs and eyes.

Least informed were stranded passengers at JFK airport's departure terminals. At American's international departure gates, the airline disclosed nothing. "They had CNN on" in the lounge, said passenger Rick Tedaldi, 31, whose Flight 679 to Aruba was canceled. "The second they showed the plane crash, [airline employees] shut the TV off. Unbelievable."

Staff writers Ceci Connolly, Guy Gugliotta, Robert O'Harrow Jr., Sally Jenkins and Chris Stern contributed to this report.