(CNN) -- Sandy Dahl, who became one of the tragic faces of 9/11 after her husband was killed while piloting United Flight 93, which crashed in Pennsylvania, died Friday.
Dahl, 52, was found dead in her home in Colorado. Jefferson County Deputy Coroner Carl Blesch said Saturday that there was no indication of foul play.
Dahl worked tirelessly running the Captain Jason Dahl Scholarship Fund and her death was a surprise, said David Dosch, a family friend.
"Sandy was instrumental in the creation of the Dahl Fund following the tragic events of 9/11, and her guiding light will be missed," the fund said in a statement posted on its website.
She died in her sleep from natural causes, it said.
The scholarship fund gives money to aspiring pilots to help them attend commercial flight training schools.
"Sandy and Jason Dahl were my best friends," said Dosch, who also works at the scholarship fund.
Jason Dahl was piloting United Flight 93 on September 11, 2001, when it crashed in a field in Shanksville, Pennsylvania. It is believed that passengers aboard that flight thwarted a plot to steer the plane through the U.S. Capitol dome and eventually caused it to crash in a field.
In an interview last year on the anniversary of 9/11, Sandy Dahl wore their wedding ring.
"I do think about him every day," she told CNN affiliate KMGH. "The reason I am doing this (interview) today and the reason that I do this at all is to make sure he is never forgotten."
CNN's Greg Morrison contributed to this report.