1st Add: Updates with FAA engine part warning

London (CNSNews.com) - Aviation experts raised questions Tuesday about the reliability of the engine on the Airbus A300-600 plane that crashed in New York, but said that an act of sabotage could not be ruled out as a cause of the crash.

The General Electric CF6, one of two types of engines that can be fitted to the A300-600, has disintegrated in mid-flight more than half a dozen times in the past two years, according to London-based Air Transport Intelligence.

Air Transport editor Kieran Daly said that during previous failures, the planes involved managed to land safely. In the most recent incident, a CF6 attached to an A300-600 failed on a Monarch Airlines flight from London's Gatwick Airport to Gambia in May of this year.

Last month, the FAA called for tougher, mandatory inspections of some parts of CF6 engines, according to Associated Press reports. The National Transportation Safety Board has also warned that failure of the engines could send metal fragments through fuel lines and could cause a crash. The American Airlines plane went through routine maintenance tests Sunday.

But Bill Gunston, editor of Jane's Aero-Engines, said that despite past incidents, the CF6 is a reliable engine.

"General Electric knows how to build engines," he said. "Basically, the CF6 is pretty good."

While U.S. officials said Tuesday that there was no sign of anything amiss in the cockpit after analysis of the plane's "black box" recorder, the possibility of an explosion - even one caused by a terrorist act - cannot be yet ruled out.

Gunston said that engines have detached from planes in the past, but that multiple engine failure raises the chances of the crash being the result of foul play.

"If both engines had fallen off at roughly the same time - that could not have happened without sabotage," he said.

Yet the theory that terrorism brought down American Airlines Flight 587 raises additional questions.

"It doesn't make much sense for explosive charges - if that's what caused the crash - to be placed near the engine," Gunston said. "It would be much more effective to place explosives closer to where the wing meets the fuselage."

NTSB decision 'premature'

Gunston indicated that there were more complex reasons behind the crash than simply an engine falling off a wing, saying that such an accident would be "survivable."

"I think it was premature to put the National Transportation Safety Board in charge of the investigation," he said. "There's a lot of unanswered questions here, and I don't think we should jump to the conclusion that this was an accident under the circumstances."

Soon after the crash, attention turned to the safety record of the Airbus A300-600, which can be fitted either with the CF6 engine or the Pratt & Whitney PW4000. On Monday, \b CNSNews.com reported that the New York crash was the ninth fatal incident -- and the fifth fatal crash - involving an Airbus 300-series plane.

Airbus planes as a whole have been involved in more than a dozen crashes over the past 13 years, but the company (based in Toulouse, France) says its planes are heavily used worldwide and that their overall safety record is excellent. The A300-600 is described by Jane's Information as "an exceptionally safe airplane."

American Airlines operates 34 other A300-series airplanes, and is one of Airbus' biggest customers. Large numbers of the aircraft are also operated by Eastern Airlines and parcel carriers UPS and Federal Express.