Accident investigators are now saying it could take months before the cause of an airplane crash in Venice that killed a Broward County doctor is finally known. The crash on Monday took the life of 63-year-old Doctor Andres Bustillo of Davie, an opthamologist and plastic surgeon who was the plane’s only passenger. The twin-engined plane crashed at the Venice airport and today, investigators from the National Transportation Safety Board are on-site, sifting through wreckage and charting aircraft parts.