The ATSB has released a 500-page final report into Australia's worst civil aviation accident since 1968. The report spells out contributing safety factors involving the pilots, the operator and the regulator as well as other safety factors, and has made further recommendations to improve future safety.

An Australian Transport Safety Bureau team of a dozen investigators has taken nearly two years of painstaking investigation to complete the final report since the tragic accident on 7 May 2005 which killed both pilots and all 13 passengers. Three ATSB factual reports, a research report and ten safety recommendations were released in the interim. The investigation was complicated by an inoperative cockpit voice recorder, no witnesses, and the extent of destruction of the aircraft.

The ATSB found that a mechanically serviceable Metro 23 aircraft operated by Transair was unintentionally flown into South Pap ridge in poor weather during a satellite-based instrument approach, probably because the crew lost situational awareness in low cloud.

The experienced 40-year old pilot in command was very likely flying the aircraft but was reliant on the 21-year old copilot to assist with the high cockpit workload. He knew the copilot was not trained for this type of complex instrument approach. Despite the weather and copilot inexperience, the pilot in command also used approach and descent speeds and a rate of descent greater than specified in the Transair Operations Manual, and exceeded the recommended criteria for a stabilised approach. The pilot in command had a history of such flying.

The investigation found significant limitations with Transair's pilot training and checking, including superficial training before pilot endorsements and no 'crew resource management'. Deficiencies also existed in the supervision of flight operations and standard operating procedures for pilots. There were also significant limitations in the way Transair managed safety, Transair's management processes and because the chief pilot was over-committed with additional roles as CEO, the primary check and training pilot, and working regularly in Papua New Guinea.

The regulatory oversight was also not as good as it could have been, especially when Transair moved from a charter to a regular passenger transport operator and was growing rapidly in Australia. In addition to the serious pilot and company contributory factors, if CASA's guidance to inspectors on management systems and its risk assessment processes had been more thorough, the accident may not have occurred.

The ATSB investigation also identified a range of other safety issues which could not be as clearly linked to the accident because of limited evidence. These included shortcomings in the design of the navigation chart used and the possibility of poor crew communication in the cockpit.

The ATSB hopes that this final report will assist the families and friends of those who perished in this tragedy to move towards closure, and will lead to further improvements in aviation safety to ensure that such an accident never happens again.