ST. HELENA, Calif. -- A preliminary report released Thursday on the Montana plane crash that killed 14 people -- including a St. Helena family -- two weeks ago said the pilot twice asked air traffic controllers to divert from the flight's original destination but gave no reason either time.

The National Transportation Safety Board's report said an eye witness with aviation experience told investigators he saw the privately owned single engine turboprop just west of the centerline of runway 33 at the Bert Mooney Airport in Butte, Mont. The report said the witness described the aircraft banking to the left and flying farther west, then it rolled, pitched down and descended out of view.

The report said the last known radio communication from the pilot of the Pilatus PC-12/45 was that he was preparing to land on runway 33. He had twice told air traffic controllers he was diverting from the flight's original destination of Bozeman to Butte,

The plane crashed into a cemetery just west of the approach end of the runway, the report said. The accident was reported to local authorities at 4:33 p.m. EDT.

Relatives said the seven adults and seven children aboard were en route to a ski vacation in Bozeman. The flight originated in Redlands, Calif., flew to Vacaville, Calif., where passengers were picked up. The pilot then flew to Oroville, Calif., where additional passengers boarded the aircraft.

Among those killed were Dr. Erin Jacobson, 37, his wife Amy, 35, and their three young children - Taylor, 4, Ava, 3, and Jude, 2, all from St. Helena.