Vince Reffet, the "Jetman" who died in a training accident in Dubai last year, lost control while hovering and did not deploy his emergency parachute, said the findings of an inquiry released Thursday.
The Frenchman had pulled off a series of dramatic flights over the Gulf city, using jetpacks and carbon-fibre wings to soar above the world's tallest building Burj Khalifa and alongside a passenger jet.
The fatal accident in November, at the Jetman team's base in the desert outside Dubai, occurred during training for a stunt where Reffet was to land on a high platform, the UAE's aviation authority said.
As a helicopter hovered at an altitude of 800 feet (250 metres) to mark the simulated height of the landing platform, Reffet entered a hover but went into a "back-leaning attitude" before flipping backwards and descending steeply.
Cameras fitted to the jetcraft showed he attempted to regain control instead of deploying his emergency parachute, the General Civil Aviation Authority said in its report.
"The loss of the Jetwing control due to an unrecoverable back-leaning attitude during hover... resulted in an abrupt flip backwards, steep descent, and ground impact," it said.
"The pilot did not abort the flight by deploying the pyro-rocket emergency parachute" as planned, it said, adding "the investigation could not determine the reasons why the pilot did not abort the flight."
The inquiry found the highly skilled pilot was not suffering from any incapacitation that affected his performance, and there was no trace of any drugs or alcohol.
"Jetwing operation is a new type of flying that utilises new technology with associated hazards and risks, which are sometimes only identified during the testing in real flight scenarios, when ground tests with safeguards are exhausted," it said.
Jetman Dubai did not immediately respond to requests for comment.
Reffet's carbon fibre wings were powered by four mini jet engines.
The equipment, which is controlled by the pilot's movements, is capable of reaching speeds of 400 kilometres (250 miles) per hour.
The Frenchman's exploits went viral at the height of his fame, with video of him taking off from the ground and climbing to 1,800 metres (nearly 6,000 feet) over Dubai's waterfront, in a feat hailed as a world first.
Reffet hovered five metres above the waters of Dubai's coast before shooting off into the air and skimming the city's skyline.
The Jetman team also includes fellow Frenchman Fred Fugen and Emirati pilot Ahmed Al Shehhi.
In 2019, Reffet and Fugen also flew through the famed "Heaven's Gate" archway in the mountains of China's Hunan province.