"RELAX, folks" says one official, speaking to millions of disbelieving television viewers. "Accidents happen. This one isn't bin Laden's handiwork."

But after the terror of September 11, which left an outraged United States, and New York in particular, feeling nervous and vulnerable, paranoia is understandably to the fore.

One eyewitness caller to a local radio station talks of a missile knocking American Airlines Flight 587 out of the skies over the suburb of Rockaway Beach.

Others report seeing an explosion which caused the Airbus to shed one of its two engines and "drop to the ground like a kite".

A key to the paranoia is that Americans are used to having safe skies. Before September 11, about 20,000 commercial flights a day took off and landed across the US, almost always without incident.

Despite fears of another fanatical terrorist attack, both the White House and the vast majority of aviation experts increasingly point towards a mechanical failure.

One Government official reports there were no threats against airplanes nor any "abnormal communications" from the doomed airliner.

Several officials underline the point by repeating that there is no evidence of terrorism.

One of the few to suspect that a bomb may have cause the explosion is former British Army officer and consultant Mike Yardley.

He believes terrorists may simply have changed tactics after the tightening up of security against potential hijackers.

"The balance of probabilities given September 11 is that it could be an attack rather than an accident.

"They could have changed their tactics because of the increased security. It has become harder to hijack a plane but not necessarily to introduce an explosive device," he adds.

Pointing out that the tragedy occurred on Veterans' Day - the US equivalent of Remembrance Sunday - he claims it is "all too easy" to plant a bomb on a plane.

But if not an act of murderous terrorism, then what?

One of the main suspects for the National Transportation Safety Board - usually assisted by the FBI until "criminal activity" is ruled out - will be the American-built engines, which have a history of problems, with seven "fairly serious" incidents in the last two years.

The CF6, made by America's General Electric company, has had a number of "fairly dramatic failures", says Kieran Daly, editor of the Internet news service Air Transport Intelligence.

In an incident in May this year, a Gambia-bound, CF6-engined Airbus A300-600 operated by UK holiday airline Monarch had to divert to Casablanca after developing engines problems while cruising over Portugal.

An investigation discovered that one of the compressor blades within the engine had broken loose due to cracking and caused damage that was not just confined to the engine area.

The most critical phases of flight are take-offs and landings when the engines are under most stress. It is also the time when a pilot has the least room to manoeuvre.

General Electric insists that the CF6 six engine was "the best in the industry".

"There have been a finite number of engine failures over the years but the problems have been identified and all the issues have been corrected," said a spokesman.

"It would be grossly premature to blame the engine for this crash."

The plane's maintenance record will also be thoroughly scrutinised to see if anything could have been left undone by ground crew which would have resulted in the sort of mechanical failure needed to down the plane.

Reports say that the plane had been in service for about 13 years - which means age is unlikely to be an issue.

Crash investigators will be able to recover almost all of the aircraft and a thorough examination of the wreckage will determine the cause of the explosion. The US will breathe a sigh of relief if terrorism is ruled out, but whatever the cause, it only adds to a heightened horror of the skies.

As one Queens resident said: "Just on the heels of one horror, another.