WASHINGTON - Federal safety officials concluded a month ago there was an unsafe condition in the type of engine that powered an airliner that crashed in New York City, and started moving toward tougher inspections.
Investigators were treating Monday's crash of American Airlines Flight 587 as an accident. The chief reason, said George Black, an investigator with the National Transportation Safety Board, is the plane's cockpit voice recorder.
"It is absent of any extraneous noises or acts that we would not associate with a normal aviation environment," Black said on CBS' "The Early Show."
However, he added on NBC's "Today" that the evidence on the recorder does not rule out sabotage. "We're not going to exclude that possibility until the investigation goes much further than this, but right now there's no evidence."
A source close to the investigation said the board also was looking at whether the engines failed after ingesting birds. Kennedy Airport, running along Jamaica Bay, has had problems with birds on the runway.
"That's a runway that's prone to having birds loafing on it," aviation consultant Jim McKenna said. "The Port Authority's always running trucks down the runway. They have fireworks cannons mounted along the length of the runway to scare the birds."
Early evidence pointed to mechanical failure in the Airbus A300 -- a plane whose CF6-80C2 engines have drawn close scrutiny since the spring of 2000, when planes reported engine failures that sent metal fragments flying.
After extensive review, the Federal Aviation Administration published a safety notice in the Federal Register on Oct. 5 stating there was a need for mandatory inspections of the CF6-80C2 engine because "an unsafe condition has been identified." It gave the public 60 days, until Dec. 4, to comment before ordering the more extensive and more frequent inspections.
The CF6-80C2 that powered the ill-fated American plane is used on more than 1,000 aircraft worldwide, including the Boeing 747 jet used by President Bush.
General Electric, parent company for the engine maker, said it complied with all the government's repair orders and believed the engine was "phenomenally reliable."
GE has built 2,954 of these engines -- first introduced in 1984 -- and they are among the best-selling for wide-bodied aircraft.
The left engine that apparently failed in Monday's crash had been overhauled recently, while the right engine was due for an overhaul soon.
Mindful of the Sept. 11 suicide hijackings of four airliners, investigators looking at Monday's crash in the borough of Queens said the voice cockpit recorder, debris patterns and eyewitness reports all pointed toward an accident, not terrorism.
"All indications are it's an accident," said NTSB Chairwoman Marion Blakey.
With the holiday travel season approaching, officials in Washington sought to manage renewed anxiety about the safety and financial health of airlines already badly shaken by the terrorist attacks.
Top administration officials were quick to stress that an initial review of intelligence data had found no evidence that terrorism was involved in the crash, and that the NTSB, which investigates transportation accidents, was in charge. The FBI assisted, looking for any evidence of a crime.
"If we find out it is a tragic accident, everybody will give a collective sigh of relief, which really shows how much stress we're under since Sept. 11," said Darryl Jenkins, director of George Washington University's Aviation Institute.
Investigators, nonetheless, scoured records of who had access recently to the plane, which had routine maintenance the night before it departed New York's Kennedy Airport en route to the Dominican Republic.
The plane's tail fin was found in the waters of Jamaica Bay.
Investigators also had extensive descriptions from eyewitnesses, including a commercial pilot on the ground who reported one of the plane's engines caught fire during takeoff and eventually broke from the wing.
"When you see an engine separate like that and be visibly intact, it seems to point to mechanical failure," said aviation lawyer Don Nolan, whose Chicago-based firm represented victims of United Airlines Flight 232, which crashed in 1989 in Sioux City, Iowa, after an earlier version of General Electric's CF6 engine came apart in flight.
The Oct. 5 FAA order came after the FAA told airlines in June to begin other inspections of the same engines for cracks in certain rotor disks, a component within the engines.
A month earlier, a problem with the same type of engine forced the emergency landing of a Monarch Airlines passenger jet in Portugal.
Documents from the British Air Accidents Investigation Branch said a rotor blade snapped, puncturing the engine's housing with a 3-inch hole and causing minor damage to the wing.
The pilots reported dramatic vibration, and British officials reported there had been "several similar failures prior to this event."
In September 2000, part of a GE CF6 series engine was ejected and penetrated the left wing of a US Airways jet undergoing a maintenance run on the ground at Philadelphia International Airport. A loud explosion was heard, following by a fire.
"This incident raises serious safety concerns because, if it had occurred during flight rather than on the ground during maintenance, the airplane might not have been able to maintain safe flight," the NTSB said in December.
Last year, the FAA ordered airlines to replace a fuel tube within these engines to prevent high-pressure leaks that investigators warned could result in an engine fire and damage to the airplane. Also last year, the FAA ordered carriers to replace certain fan shafts earlier than planned to prevent possible catastrophic failure.