December 9, 2011, Sioux Falls, S.D., Cessna 421C

At 1424 Central time, the airplane was substantially damaged when it impacted terrain shortly after takeoff on a Part 135 on-demand air taxi flight. The commercial pilot and the three passengers were fatally injured. Visual conditions prevailed.Shortly after takeoff, ATC informed the pilot a smoke plume was visible behind the airplane. At 1424, the controller cleared the flight to land. No communications were received from the pilot after he acknowledged the takeoff clearance. Witnesses observed flames at the inboard side of the left engine.