The Shoreham air disaster was caused by the pilot flying too slowly and too low during a loop manoeuvre, accident investigators have said.
Eleven people were killed and 13 injured on 22 August, 2015, when Andrew Hill, 52, crashed in a vintage jet onto the A27 in West Sussex during an air show.
The final report by the Air Accidents Investigation Branch (AAIB) stated that the speed the 1955 Hawker Hunter was doing when it entered the manoeuvre was too low, and it failed to use maximum thrust.
The AAIB also concluded that measures taken to mitigate the effects of an aircraft crashing outside the boundary of the air show were “ineffective” and contributed to the severity of the death toll.
Responding to the report, Sue and Phil Grimstone, the parents of victim Matthew Grimstone, 23, said the Civil Aviation Authority (CAA) and the air show organisers “have got much to answer for”.
In a statement, they said: “Apart from anything that the pilot may have got wrong, it is very evident the CAA and the Shoreham Air Show organisers have got much to answer for. Rules laid down by the CAA were quite clearly inadequate and those that were there were, in some cases, not fully adhered to by the air show organisers.”
Mr Hill, from Sandon, Hertfordshire, suffered serious injuries. He is being investigated by Sussex Police for possible manslaughter.
Following the publication of the AAIB report, the force said it hopes to submit a file of material to the Crown Prosecution Service by 20 June.
Flight trials indicated that Mr Hill, a former RAF pilot, could have pulled out of the stunt up to four seconds after reaching the top of the loop, but he either did not perceive it was necessary or did not realise it was possible.
He had not received formal training to escape the manoeuvre and had not had his competence to do so assessed, the report found.
The speed, height and thrust followed in the Hunter were “very similar” to a Jet Provost that the pilot had flown during displays in the run-up to the Shoreham event, AAIB principal inspector Julian Firth said.
He added that it was possible “the pilot recalled the wrong numbers, essentially mixing up the two aircraft”.
Mr Hill was interviewed on seven occasions by AAIB investigators, but could not remember events between 19 August and regaining consciousness in hospital.
Organisers of the Shoreham air show said it was unlikely they will stage such events in the future.