What happened
On a scheduled charter flight from Cairns to Hicks Island, an aircraft departed at 07:07 EST under Instrument Flight Rules (IFR). Shortly after the departure, the pilot requested permission to descend to an altitude of 4,000 ft, stating that visual contact with the ground or water could be maintained. Air Traffic Services (ATS) granted this request, despite the IFR Lowest Safe Altitude for that specific route sector being 6,000 ft AMSL.
Approximately 13 minutes into the flight, the aircraft vanished from radar surveillance while traveling at a ground speed of 180 knots. The last recorded position was 46NM north of Cairns at the requested 4,000 ft altitude. Following an extensive search operation, wreckage was discovered the next afternoon on the northwestern slope of Thornton Peak at an elevation of roughly 4,000 ft AMSL. The impact and subsequent fire caused the total destruction of the airframe. The crash resulted in four fatalities, comprising the pilot and three passengers.
Witnesses observed the aircraft roughly two minutes before the collision. They reported the plane was flying at a high speed on a steady north-westerly course with the landing gear and flaps retracted. The engines were noted to be operating normally at the time of observation.
Findings
Investigation into the circumstances noted that the aircraft was operating at an altitude below the established IFR Lowest Safe Altitude for the sector. Additionally, Thornton Peak, which stands at 4,507 ft, is frequently obscured by heavy cloud cover and high winds, which may have impacted visibility during the flight.