The crash of a Trans World Airlines 747 into the waters off Long Island could well heighten America's feeling of vulnerability to sudden and tragic events.
First came the ValuJet disaster in the swamps of the Everglades. Then a powerful bomb devastated US troops based in Saudi Arabia. Now a third calamity in a matter of months has emphasized that for all its superpower strength, the US is not immune to the quick strike of tribulation.
If the TWA crash is proved to be an accident, the airline industry may have to work hard to regain public trust already shaken by the ValuJet incident. If its cause turns out to be a bomb it would represent a major increase in the level of terrorism directed at US targets.
"It seems we are becoming a more central target for various [terrorist] groups that may not necessarily be coordinated. But it seems premature to reach any conclusions," says Uri Ra'anen, director of the Institute for the Study of Conflict at Boston University.
TWA Flight 800, a 25-year old Boeing 747 traveling from New York's Kennedy Airport to Paris, exploded with 228 people on board. As of this writing no survivors had been found.
The Federal Bureau of Investigation (FBI) is investigating the cause of the crash, in concert with the New York Police Department. The National Transportation Safety Board is also probing the crash.
The quick involvement of the FBI and other antiterrorist experts caused many to speculate that the government believes the disaster was caused by a bomb.
If a bomb was placed on flight 800 as it sat on the ground in New York, it would mark the first such successful terrorist attack mounted from US soil.
But some bits of evidence indicated that mechanical failure might have caused the accident. Eyewitnesses described a small flame, followed by a large explosion - perhaps indicating an engine fire that burned through a wing fuel tank.
One Boeing engineer, however, said Thursday that he and his colleagues were having difficult imagining what chain of mechanical failures could have caused Flight 800's quick plunge from the sky. Wind blowing past an airplane in flight would likely snuff out an engine fire, he said - though he added that the pins holding the engine to the airframe have caused problems on 747s in the past. At least one of the jumbo jets has crashed in the past due to pin failure.
Furthermore, Flight 800 was a 747-100 model which entered service in 1971, making it one of the oldest jumbos still operating.
"Airplanes wear out and fail a lot more when they get old, just like cars," says the engineer.
Overall, however, the 747 is one of the safest airplanes to ever take to the skies. Its hull loss accident rate is 1.64 accidents per million departures, compared to 1.83 accidents per million departures for all big commercial jets, according to Boeing statistics.
Security specialist Neil Livingstone says that the evidence made public so far his hunch is that Flight 800 was indeed destroyed by a bomb. Determining whether a bomb-caused internal explosion downed the plane, as opposed to an engine-caused external explosion, is a simple but tedious process, he points out. Metal debris will reveal internal pitting and scoring if a bomb went off inside the cabin or cargo bay.
Piecing together the chain of evidence as to what really happened in the air off Long Island could take a considerable amount of time. Solving the mystery of Pan Am Flight 103, which exploded over Lockerbie, Scotland, in 1988, took over four years.
"The key to most of these bombs is detonation," says a former CIA analyst who was involved in the Lockerbie investigation.
In the case of Pan Am 103, a barometer caused the bomb to explode once the plane reached a certain altitude. Flight 800 exploded at a similar point in its planned flight - as it reached a fairly high altitude and began to cruise towards its destination.
The financial implications for TWA are still unclear. But the explosion comes at a time when the St. Louis-based carrier was pulling out of an economic tailspin. After twice going into bankruptcy, the airline reported strong quarterly earnings on Wednesday.
If this was indeed an accident, it is the first of a major US air carrier this year. Experts in the airline industry were quick to jump on the FAA after the ValuJet crash in May, critizing it for its lax oversight of low-fare carriers.
Since, the FAA has transferred much of its focus to oversight of start-up airlines, which contract out much of their mechanical work. But TWA is a well-established carrier. If the explosion was caused by a mechanical failure, the FAA's inspection teams may face additional scrutiny.
Frequent flyers may think twice about flying as well. Travel consultants say they didn't experience a great change in traffic patterns after the ValuJet crash. But after a USAir 737 crashed in Pittsburgh in 1994, there was an immediate flight to other carriers. "If it's a national carrier, you tend to get a little more [cancellations],"says Gayl Heinz, vice president of Caboose Travel Service in Beverly, Mass.
*Robert Marquand contributed to this report.