SILVERTON, Colo. (AP) — Federal investigators say the weather was changing rapidly over Silverton, Colo., before a small passenger plane crashed in December 2011, killing all four people on board.

The National Transportation Safety Board says the pilot told an air traffic controller he was not rated to fly a plane using only instruments for navigation.

The agency says the pilot asked for the controller's help moments before the plane disappeared from radar and contact was lost.

The Durango Herald reports (http://tinyurl.com/bndlgmd ) the pilot, Steve Osborne, and his three passengers were killed. All four were from Durango. The passengers were Tyler Black, Gena Rych and Osborne's wife, Jan Measles Osborne.

They were en route from Durango to Aspen to attend a party for Alpine Bank.

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Information from: Durango Herald, http://www.durangoherald.com