Federal investigators say the pilot and a passenger spent three hours clearing snow and ice off of a small plane before it crashed after taking off from a small South Dakota airport over Thanksgiving weekend.

The Nov. 30 crash killed nine of the 12 members of an Idaho family who were on board, including the pilot.

The National Transportation Safety Board says in a preliminary report released Tuesday that three of the planes warning systems activated within seconds of taking off from the small airport in Chamberlain, South Dakota.