An online obituary said the plane broke up in flight. An employee, Jacob Curiel, age 28, was also killed.
According to a preliminary report by the National Transportation Safety Board, the debris path was more than a half-mile long, with "the cabin separated into several sections that were scattered throughout the center" of the field.
Johnston and his wife and bookkeeper, Evelyn M. Quaresma, founded the family-owned firm in 1969. It specializes in cast-in-place underground concrete pipelines for water and wastewater municipal clients in northern California. Daughter-in-law Karen Johnston became controller in 1988.
The union firm completed a $17-million outfall system in Tracy, Calif. in 2004 and was recently awarded a $5.4-million water transmission line in Fresno, according to a local report. It has $17 million to $23 million in annual revenue and about 80 employees. The firm will continue, officials say.