JULIAN, Calif. -

The San Diego County Sheriff's Department launched a search for small airplane in rugged terrain Wednesday night after the aircraft failed to land in San Diego as expected.  Deputies said that at around 6:15 p.m. officials from Gillespie Tower reported that the airplane, described as a single-engine Piper Mooney traveling from Palm Springs, Calif., to San Diego, had lost contact while flying over the Julian area in San Diego's East County.  Officials say the last known location from the air control tower puts the aircraft near the Volcan Mountain Wilderness Preserve located approximately four miles northeast of Julian.  The Sheriff's Search and Rescue Team (SAR) immediately launched a search for the private plane. However, the rugged, mountainous terrain made it challenging. The sheriff's ASTREA helicopter attempted to assist in the search by air, but due to inclement weather, ASTREA had to cease their attempted search efforts. Deputies say that as soon as weather permits, ASTREA will return to aid in the efforts. As of 10:30 p.m., officials said a command post had been established at the Julian Sheriff's Substation located at 2907 Washington St. Deputies, as well as Civil Air Patrol, will remain at the scene. Officials say it is unknown how many people were aboard the aircraft, but the plane was due to land in San Diego at around 6:15 p.m. On Wednesday, wind, rain and dense fog swept San Diego County - the first weather of this kind this season. At night in Julian, visibility on the ground was less than 50 feet due to dense fog.