A plane crash that killed three people while conducting a fire surveillance operation in outback Queensland in 2023 was due to the pilot suffering from a severe lack of oxygen caused by a defect in the aircraft, a transport safety report has concluded.

The Australian Transport Safety Bureau report found that the aircraft’s steep descent and ultimate impact with the ground was almost certainly due to the pilot being hypoxic due to a known defect with the aircraft’s pressurisation system.

ATSB Chief Commissioner Angus Mitchell released the report (on 19 June 2025) with the conclusion that the incident should have been prevented. “This was a tragic and entirely unnecessary accident that underscores the dangers of operational practices which circumvent critical safety defences, and the insidious and deadly potential of altitude hypoxia.”

The AGAIR‑operated twin turboprop Gulfstream 695A (a variant of the Aero Commander aircraft series) was mapping fire zones near Mount Isa on 4 November 2023, with a pilot and two camera operators on board, including 22-year-old William Jennings from the United States. The other two people on board the aircraft have not been publicly identified, although the ATSB report states that the pilot had a total of 4900 hours flying experience, including with high-performance Royal Australian Air Force military aircraft. The pilot had only joined AGAIR in August of 2023 and at that time had not previously flown a Gulfstream 695A but subsequently undertook training.

The report found: “Over a period of many months, the accident aircraft’s pressurisation system was not reliably maintaining the required cabin altitude. This led some company pilots to employ a variety of actions in the aircraft to manage the potential and deadly effects of hypoxia, including at times briefly descending to lower altitudes, and improperly using emergency oxygen systems,”.

The ATSB found that the aircraft had a long-term intermittent defect with the pressurisation system that would manifest as a reduced maximum attainable cabin differential pressure. The report noted that the defect was known by senior AGAIR management who attempted to have the defect rectified. However, the ATSB concluded, they did not formally record the defect, communicate it to the safety manager, undertake a formal risk assessment of the issue, or provide explicit procedures to pilots for managing it. 

“The ATSB found the onset of hypoxia during the flight significantly degraded the pilot’s ability to safely operate the aircraft, and it is possible that at stages the pilot also experienced some loss of consciousness,” Mr Mitchell said.

Air traffic control recordings of the pilot’s speech during the accident flight demonstrated significant and progressive impairment, including slowed, stuttering and flat speech, operational mistakes and signs of confusion.

“Hypoxia can occur when an individual is exposed to high altitudes, typically above 10,000 ft, when not enough oxygen is supplied to the blood, tissues and cells for the body and brain to properly function,” Mr Mitchell said.

ATSB has issued a formal safety recommendation to AGAIR to initiate an independent review of its organisational structure and oversight of operational activities to implement ongoing effective operational control by management.

Read the final report: Pilot incapacitation, loss of control and collision with terrain involving Gulfstream 695A, VH-HPY, 55 km south-east of Cloncurry Airport, Queensland on 4 November 2023