Investigators of the crash which killed 230 people in the Boeing 747- 100 on July 17 when the plane exploded soon after take-off from New York are close to deciding that the disaster was caused by mechanical failure rather than a bomb.
If the cause is confirmed as mechanical failure, the implications for airlines are extremely worrying. There are more than 1,000 Boeing 747s, and more than 700 of them are early versions such as the one involved in the TWA disaster. While the finding of a bomb would have led to the usual requests for better security at airports, the prospect of a mechanical fault having caused the disaster raises the possibility of large-scale changes being made to the world's "workhorse of the skies".
Investigators have also not found a cause for the loss of the Peruvian Boeing 757 which plunged into the sea earlier this month killing all 70 people aboard.
Three months after the New York disaster, and with no definitive statement about a bomb, the likelihood of a terrorist attack having caused the accident recedes.
It took investigators only a few days after the 1988 Lockerbie to decide that a bomb was the cause, because traces of chemicals that could only have come from a bomb were found. While the job of the investigators of the TWA crash was made more difficult because all the debris was in the sea, more then 90 per cent of the plane has now been recovered and there is no evidence of a bomb.
The investigators have pinpointed a centre fuel tank on one of the wings as the site of the explosion which destroyed the plane and, despite 80 per cent of the tank having been recovered, no trace of an explosive device has been found. In fact, metallurgical tests are much more suggestive of a mechanical failure than a bomb.
According to a report in yesterday's Washington Post, investigators say that tests have shown that parts of the fuel tank were blown outward, suggesting the blast occurred inside it. And they have found no sign of any metal pushed in towards the tank which would be the case if a bomb had been hidden nearby in the cabin.
The Post reports: "Safety investigators say that a mechanical malfunction now seems a more likely explanation for why Flight 800 went down."