The pilot and eight parachutists were returning from a skydive meet. The pilot had obtained a weather briefing, which advised of instrument meteorological conditions at the destination, and filed a VFR flight plan, but it was never activated. Witnesses heard, but could not see, a twin engine turboprop pass over the airport, heading north out over the Great Salt Lake. They described the weather conditions as being a low ceiling with 1/4-mile visibility,