A fast-moving fire from damaged wires in the cockpit of Swissair Flight 111 raced through the flammable insulation used inside the aircraft, spreading so rapidly that the pilots of the MD-11 would have had no time for a safe landing even if they had been alerted to the fire earlier, Canadian officials concluded in a report released Thursday.

The Geneva-bound flight crashed in the sea near Nova Scotia on Sept. 2, 1998, killing all 229 on board.

When the flight crew noticed the smell of smoke in the cockpit, 53 minutes after taking off from Kennedy Airport, they thought it was coming from the air-conditioning system and began running through an emergency checklist to fix the problem as they made arrangements to land at the nearest airport. Nine minutes later, the aircraft began to lose crucial flight control systems due to the fire. Twenty minutes after the crew noticed the smoke, the plane was uncontrollable and pitched nose down into the Atlantic Ocean. Swissair, once one of the world's elite carriers, is now in bankruptcy.

After an investigation that lasted more than four years, the Transportation Safety Board of Canada concluded that it was the presence of flammable insulation blankets lining the fuselage that turned the wiring problem into a tragedy.

"An arcing event or events provided an ignition source for the fire; however, this arcing would not have resulted in a threat to the aircraft had there not been material nearby that could easily be ignited," said the TSB report. The insulation blankets that caught fire were coated with a material called metallized Mylar that easily catches fire; the suspect insulation was used on more than 700 U.S.-registered aircraft. The insulation protects the interior from temperature changes and reduces noise.

In May 2000, the Federal Aviation Administration ordered U.S. airlines to remove the metalized Mylar insulation after the Swissair crash. But the agency gave the airlines five years to accomplish the task, and it's not clear how many planes are still flying with the material. FAA spokesman Les Dorr Jr. said the work was to be done during an aircraft's so-called heavy check, a major overhaul done once every few years, because ripping out the insulation involves dismantling the plane's interior.

The scope of the investigation was daunting. Canadian investigators recovered 98 percent of the aircraft -- more than 2 million pieces -- including most of the 155 miles of wiring in the plane. They reconstructed a three-dimensional mock-up of the cockpit and forward cabin to better understand the fire damage. From that, they were able to show that the fire started in the rear right cockpit ceiling, near the wall that separates the cockpit from the cabin.

The fire was sparked by wires that were either chafed or damaged to the point that the insulation was worn off the copper core. When the electrical current jumped from one copper core of the wire to another, it created sparks and ignited the insulation blankets.

Investigators said one of the wires involved was connected to the in-flight entertainment system that had been installed in business and first-class sections. But they weren't able to show for sure what other wires were involved.

As in all aircraft crashes, it was a chain of events that led to the disaster. But the TSB found that the most significant link in the chain was the flammable insulation blankets. "Without the presence of this and other flammable materials, this accident would not have happened," Vic Gerden, the chief investigator on the Swissair crash, told a Halifax news conference.

The report also criticized the FAA's process of certifying materials. The agency's fire research had traditionally focused on materials that burn easily inside the cabin, so the most stringent flammability tests were applied to things like seats and wall panels. But the insulation blankets, placed between the panels and the fuselage, run near wire bundles that can spark fires. Yet the flammability requirements for the insulation were much less rigorous. The FAA said it has begun an accelerated research program looking at other flammability issues.

"The certification testing procedures mandated under flammability standards ... were not sufficiently stringent or comprehensive to adequately represent the full range of potential ignition sources," the report said. "Had the pilots been aware that flammable materials were present in the attic space of the MD-11, this knowledge might have affected their evaluation of the source of the odour and smoke."