Pilot Andy Hill was 'may not have been in control of what he was doing' when his Hawker Hunter jet tragically crashed in Shoreham in 2015.
Hill, 54, of Standon Road, Buntingford, is standing trial for 11 charges of manslaughter by gross negligence. You can follow the trial live here.
Mr Hill's defence barrister Karim Khalil QC said his client was not in control of the aircraft during the fateful 'bent loop' manoeuvre.
He told the court: "He is not a cavalier pilot and is not a pilot who was - as has been suggested - playing fast and loose with the lives of onlookers.
"We say that this may not have been about pilot error at all because Andy Hill may not have been in control of what he was doing."
He argued that the flightpath of the Hawker Hunter jet shows that his client was cognitively impaired.
"A proper analysis of the last manoeuvre leads one to the conclusion that he was suffering from cognitive impairment and he was not in full control of his actions.
"Nobody could have made those various errors if they were fully in control of what they were doing and was aware of the situation that was developing. They were simply too numerous.
The flightpath in the last moments diverts so remarkably from what had been planned to be explained by a pilot making mistakes.
"The features of the flying that occurred during that fateful manoeuvre are as a result only capable of being satisfactorily explained if the pilot was suffering from cognitive impairment."
Prosecutor Tom Kark QC however said there is 'clear evidence' to suggest that Hill was in control of the plane.
He told the trial : "There is clear evidence to suggest that Mr Hill was conscious and in control of the aircraft during and throughout the manoeuvre.
"The aircraft crash a as a result of Mr Hill's negligence and such this breach of duty caused the deaths of 11 men."
The trial continues