The pilot in the Frankie Dettori aircraft crash had not been trained to use the type of plane involved in the accident, an accident report says.
Patrick Mackey, 52, died in the crash at Newmarket Racecourse last June. Dettori and fellow jockey Ray Cochrane escaped from the wreckage.
Mr Mackey usually flew a Cessna aircraft, but this plane was unavailable, so he had been using a Seneca plane for a few days before the crash.
The Air Accidents Investigation Branch report said there was no record of the pilot having received training on a Seneca.
He had also not practised engine failure or shutdown procedures on the Piper Seneca aircraft.
But the report said there was no requirement for him to have done these manoeuvres.
Mr Mackey had been carrying jockeys to race meetings for the previous two seasons and had flown from Newmarket on many previous occasions.
The AAIB report said it was Mr Mackey's normal practice to use a 10 degree setting for the aircraft flaps when taking off on grass with the Cessna 303.
The report said that it was probable that this setting was used on the Seneca on the day of the crash.
But it added: "For the Cessna 303, with which the pilot was familiar, take-off techniques differed from the Seneca in some respects".