The six-woman jury deliberated for more than six hours after listening to more than a month of testimony.
Stewart won the U.S. Open, his third major victory, just months before his death.
His widow, Tracey, and their two children sued Learjet, claiming a cracked adapter caused an outflow valve to pull away from the plane's frame, resulting in a decompression and the escape of cabin air as the plane climbed to its flight altitude after leaving
Orlando on Oct. 25, 1999. All communication with the plane was lost soon afterward and it flew on for hours, all aboard presumably unconscious, until it crashed in South Dakota.
The family sought $200 million.
Attorneys for Learjet told the jury that the plane lost pressure in another way and that damage to the valve was caused by the crash.
They also said the plane was poorly maintained by Sunjet, the now-defunct central Florida company that operated the Learjet.
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