Two weeks after ValuJet Flight 592 plunged into the Florida Everglades, the bits of evidence pulled from the murky swamp have yet to produce a clear picture of what went wrong.
From the clues that have been assembled, federal investigators now believe either a fire or an explosion in the plane's cargo hold caused the crash, which killed the 105 passengers and five crew members.
But the fact remains that the National Transportation Safety Board (NTSB), in charge of the investigation, still doesn't know for certain what caused the accident.
There has been plenty of speculation, of course. During the past two weeks, the media have focused public attention variously on ValuJet's maintenance practices and the age of its fleet, the adequacy of the Federal Aviation Administration's inspections of ValuJet aircraft, oxygen tanks in the plane's cargo hold and the shipping company that labeled them, and ValuJet pilots - none of which may turn out to be relevant.
"It's really very seldom those things that get the early attention actually end up being what caused the accident," says Clinton Oster, professor at Indiana University in Bloomington and co-author of "Why Airplanes Crash."
"There's been almost a preoccupation with the crew and the age of the aircraft - even though we haven't seen any evidence that the age had anything to do with the cause of this accident," he says. Investigators "have to recover more of the aircraft, including the voice recorder, before they can determine what caused this."
Hampered by adverse conditions such as muck, cloudy water laced with jet fuel, alligators, and poisonous snakes, the NTSB says it may take several months to determine the precise cause of the crash.
Investigators Thursday called in dredging equipment in an effort to turn up more parts of the aircraft. So far, about 25 percent of the DC-9 has been recovered: both engines, the plane's flight-data recorder, and parts of oxygen tanks that were in the plane's cargo hold - including pieces embedded in a tire.
As many as 136 small oxygen generators, which are used to provide oxygen for passengers' emergency masks, were being transported in the plane's forward cargo bay, along with three airplane tires. These canisters, which produce intense heat when activated, are suspects in a fire that may have occurred on board before the plane went down. The tanks presumably were empty and, therefore, not a threat to safety. But if some still contained chemicals, investigators say it's possible the tanks may have been ignited, causing a fire or explosion.
The Department of Transportation announced Thursday that no airline will be permitted to transport oxygen generators as cargo until the DOT completes an investigation into the safety hazards they pose. ValuJet was not authorized to carry these "hazardous" materials.
The ValuJet crash has focused attention not only on the three-year-old carrier, but also on the entire discount-airline industry. Even so, observers caution against a rush to judgment. "When all the facts come out, we will probably find it was an extremely subtle mistake," says statistician Arnold Barnett, who studies aviation safety at the Massachusetts Institute of Technology in Cambridge, Mass. "If you were to board a jet in the US every single day, on average you would go 21,000 years before succumbing to a fatal crash."
In the tense days after the crash, ValuJet was the first to come under scrutiny. The airline was founded in 1993 with just two DC-9s. The low-fare carrier today has 47 of the McDonnell Douglas aircraft and flies to 26 cities. Its meteoric growth has been attributed to its no-frills flights. Passengers do not get tickets or meals. Flight attendants wear khakis and Polo shirts rather than uniforms.
But some of ValuJet's other cost-cutting measures have been severely criticized. The average age of its planes is 26 years, leading many to guess that engine or maintenance problems caused the crash. In addition, ValuJet does not pay its flight attendants or pilots if they don't fly. Many critics charge that pilots worried about not being paid may take more chances.
The airline, however, is not the only one being scrutinized. Inspectors for the DOT, parent agency of the FAA, have criticized the FAA for its hit-and-miss inspections of ValuJet.
The FAA has released two reports since the crash. A May 16 account compares safety records of low-cost and major airlines. It shows that ValuJet had the second-highest accident rate among low-cost carriers. The FAA did not have available copies of inspection reports for Tower Air, the airline with the highest accident rate and the one that often carries the White House press corps.
A Feb. 14 FAA memo showed the agency had recommended that ValuJet undergo a recertification process. The memo said ValuJet had 46 violations since it began flying in 1993, and 20 of those had not been resolved. The memo concluded that the FAA itself was also at fault. "The data reviewed clearly show some weakness in the FAA's surveillance," the report said. The FAA is now conducting a full investigation into ValuJet's procedures and safety standards.
ValuJet president Lewis Jordan says he is cooperating fully with the NTSB and is doing more than the FAA has recommended. ValuJet has hired a new "safety czar" and has cut its flight schedule almost in half until the FAA review is complete.