South Africa investigators are urging authorities to evaluate all ex-military aircraft flying on the civil register and mandate immediate safety inspections for their ejection seats.
The team was unable to determine the cause of hydraulic failures and an apparent in-flight fire. Stock died after his ejection seat failed to activate, a problem that also remains a mystery.
Stock's supersonic Lightning T5, registered ZA-BEX, was not equipped with a cockpit voice recorder or a digital flight data recorder, the investigation report notes.
Stock reported to the tower he was experiencing a hydraulic problem. Air show visitors also snapped photos showing an onboard fire, the report says.
Stock manoeuvred the aircraft away from the air show to an unpopulated area. At that time, Stock reported a double hydraulic failure, possibly caused by the fire, the report says. He attempted to activate the Martin Baker 4BSB NK 2 ejection seat, but the seat failed for unknown reasons.
The same aircraft experienced a hydraulic pump failure on a flight more than six years ago, the report says.