PITTSBURGH (KDKA) — Twenty years ago, on a clear, cloudless September night, US Air Flight 427 mysteriously fell from sky on its approach to Pittsburgh International Airport.

It crashed in Hopewell Township, Beaver County, killing all on board.

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What caused the plane to pitch and roll and spin out of control would become the subject of the longest crash investigation in aviation history.

“It took four years, two public hearing and thousands of investigative hours, but we were able to find the cause of that tragedy,” said Jim Hall, the former chairman of the National Transportation Safety Board.

The NTSB determined the crash to be the result of an out of control rudder caused by a defective value.

Hall spoke with KDKA on Thursday from Chicago about changes that finding brought about.

“Boeing made almost a billion dollar investment in changing the rudders on all the Boeing 737s that fly, which of course is still the most popular aircraft in the world,” said Hall.

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But above and beyond determining a cause, the families of the victims fought another battle, addressing the treatment they receive from the airline in the aftermath of the crash.

Dennis Connolly, of Brookline, lost his twin brother Robert in the crash. He said at the time airlines like US Air kept families in the dark.

“People who were at the airport to meet the flight were locked up in the US Air club and weren’t told anything. What’s going on? No one would say anything,” says Connolly. “Allegheny County wanted to get counselors in there and they wouldn’t let them in. They didn’t want you to know what was going on and they didn’t want you talking with each other.”

As a result, the families work toward the writing and the eventual passage of the Aviation Disaster Family Assistance Act, which establishes airline notification polices and requires them to provide daily briefings and counseling for families.

John Kretz, of Homestead, lost his wife Janet in the crash. He lobbied for the act and was there when President Clinton signed into law in 1996.

“Everybody went up to shake his hand, and I said thank you, and he actually pulled me back and said, ‘No, it’s us who should thank you for pushing it through.’ That was really nice and it made all that effort and grief worthwhile,” Kretz said.

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