On 4 September 2000, a chartered Beechcraft 200 Super King Air departed Perth for a flight to the mining town of Leonora, Western Australia. The aircraft crashed near Burketown, Queensland, Australia, resulting in the deaths of all eight occupants. During the flight, the aircraft climbed above its assigned altitude. When air traffic control (ATC) contacted the pilot, the pilot's speech had become significantly impaired, and he was unable to respond to instructions. Three aircraft intercepted the Beechcraft, but were unable to make radio contact. The aircraft continued flying on a straight north-easterly heading for five hours, before exhausting its fuel and crashing south-east of Burketown. The crash became known in the media as the "ghost flight".
A subsequent investigation by the Australian Transport Safety Bureau (ATSB) concluded that the pilot and passengers had become incapacitated and had been suffering from hypoxia, a lack of oxygen to the body, meaning the pilot would have been unable to operate the aircraft. Towards the end of the flight, the left engine stopped due to fuel exhaustion, and the aircraft crashed into the ground. The investigation report said that, due to extensive damage to the aircraft, investigators were unable to conclude if any of the eight aboard had used the oxygen system. The final report stated that the ATSB could not determine what incapacitated the occupants. A number of safety recommendations were made following the crash.
Background
The aircraft involved in the crash was a Beechcraft 200 Super King Air, registration VH-SKC, serial number BB-47, manufactured in 1975. The aircraft had about 19,000 hours of service before the crash. The amount of air passed into the cabin is controlled by bleed air valves on the engines. The positions of the bleed air valves can be altered by the pilot. According to the investigation report, "The aircraft was not fitted with a high cabin altitude aural warning device, nor was it required to be." The aircraft was fitted with an emergency oxygen system—an oxygen tank which could supply oxygen to the crew through two masks located in the cockpit, and to passengers through masks which drop from the ceiling of the cabin.
Investigators concluded the aircraft was airworthy at the time the crash occurred, and a pilot who flew the aircraft earlier in the day said the aircraft functioned normally. The investigation report stated that "the maintenance release was current, and an examination of the aircraft's maintenance records found no recurring maintenance problems that may have been factors in the accident."
Crash
On Monday 4 September 2000, the Beechcraft, chartered by mining company Sons of Gwalia, departed Perth, Western Australia, for the town of Leonora, Western Australia, On board were seven mine workers travelling to Gwalia Gold Mine. The aircraft took off from Perth at 6:09 pm local time (1009 Coordinated Universal Time (UTC)), and was cleared by ATC to climb to FL130 (). Five minutes later, at 1015, it was further cleared to its cruising altitude of FL250 (); with an instruction to be at FL160 () by from Perth. The pilot acknowledged this transmission.
Five minutes later, at 1020, as the aircraft climbed through FL156 (), it was cleared to waypoint DEBRA. The pilot again acknowledged. At approximately 1033, the aircraft passed through its cleared level, and at FL256 (), ATC asked the pilot to confirm his altitude. "Sierra Kilo Charlie—um—standby," the pilot replied. This was the final spoken transmission from the aircraft, and its climb continued. According to the investigation report, several open-microphone transmissions followed, with the sound of background noise from the engines, a person breathing, "one unintelligible syllable," and "two chime-like tones, similar to those generated by electronic devices." During this time, ATC attempted to regain contact with the pilot. At 1040, the controller called out, "Sierra Kilo Charlie Sierra Kilo Charlie, Melbourne Centre, if receiving this transmission squawk ident." At 1041, the controller asked again, "Sierra Kilo Charlie, only receiving open mike from you. Would you contact me on one two five decimal two."
The aircraft continued to climb, and left radar coverage at 1102, passing FL325 (). Thirty-one minutes later, Australian Search and Rescue asked the crew of a business jet to approach the Beechcraft. They reported that it was in level flight at FL343 (), and they could see no movement on the flight deck or in the cabin. However, the conditions made it difficult to observe closely.