It's quiet here now.
The whine and thunderous crack of an airplane crashing to earth have faded. Gone, too, are the sounds of rescue crews frantically searching for survivors and the crackling of campfires lit by state police to keep warm.The only sounds heard now on the hillside where USAir Flight 427 nose-dived on Sept. 8, 1994, killing all 132 on board, come from buzzing cicadas and, occasionally, the sobs of families visiting the spot where wives, husbands, sons and daughters died.
Elsewhere, though, the nation's deadliest airplane crash since 1987 reverberates.
Grieving relatives are pressing lawsuits in three cities, and striving to change the way airlines deal with the survivors of disaster victims.
USAir is still struggling - with some success - to regain its reputation as well as its financial footing. Rescue workers are still trying to recover from their nightmare experience.
And federal investigators, stymied by incomplete data and a lack of witnesses, are pressing forward in their search for a cause.
There were no witnesses and no survivors to tell them what happened in the minutes before the Boeing 737 smashed into a wooded terrain near the Pittsburgh International Airport.
The plane shattered into thousands of pieces, leaving few fragments big enough to provide meaningful clues. And while the aircraft's flight data recorder was recovered, it was an older model - one that told investigators little about the plane's control surfaces.
Nearly 100 investigators have spent more than 40,000 hours searching for an answer, drawing on experts from the United Kingdom, France, Denmark, Australia and Canada.
They have conducted hundreds of computer simulations to recreate crash conditions and made a two-dimensional structural reconstruction of the plane based on the wreckage.
Much of the probe has focused on what could have caused a sharp movement in the aircraft's rudder, which controls the direction of the plane.
Investigators have ruled out bad weather, a bomb, hitting a bird and structural failure. They speculate that another airplane about four miles ahead of Flight 427 might have created turbulence that contributed to the crash.
But dozens of tests have yielded nothing conclusive.
"It's hard to say where the end is going to be because we don't know what's going to be uncovered tomorrow," said Tom Haueter, the lead investigator with the National Transportation Safety Board.
The fact remains, though, that investigators may never definitively know what sent Flight 427 out of control.
"At this stage, the fact that they don't have a smoking gun leaves a reasonable probability there never will be a clear answer," said Charles N. Eastlake, a professor of aerospace engineering at Embry-Riddle Aeronautical University in Daytona Beach, Fla.
USAir spokesman Richard Weintraub said many employees "have spent many sleepless nights" pondering the mystery.