The Civil Aviation Authority are confirming an air incident during the Southport Airshow on 20 September, 2014, formed part of Sussex Police's on-going investigation into the Shoreham vintage jet air crash which took place almost a year later on 22 August 2015.
It has been suggested the jet Pilot Andrew Hill was flying that day was considered to be low to sustain the manoeuvre.
A spectator at the earlier show said:"Last minute, as he was approaching, he banked off to one side to avoid colliding into the crowd, and it frightened many people.
"Spectators were talking about it immediately afterwards, about how close it had got, and how fast and low the plane was.
"I remember at the time feeling, 'this is worrying, this is concerning, I need to move out the way', but luckily he managed to bank last minute."
The Air Accidents Investigation Branch is investigating what caused the 'cold war' Hawker Hunter jet to crash on the A27 in West Sussex, during the Shoreham Airshow.
The pilot Mr Hill, 51, from Hertfordshire, was thrown clear from the jet and survived the crash. He was later voluntarily interviewed under caution by police officers.
A CAA spokesman said: "We are aware of an incident that took place at the Southport Airshow in 2014 following which the CAA took appropriate action in conjunction with the show's organisers.
"We have been informed that this incident currently forms part of an on-going investigation by Sussex Police."
The CAA, which had an inspector at the event, said it had spoken to Mr Hill about the incident.
Detective Chief Inspector Paul Rymarz said families of the victims of the Shoreham disaster had been informed officers were also looking at the 2014 incident.
He added: "This incident forms a line of inquiry in our wider investigation. All the families are aware of our interest in this incident."
The Shoreham crash was the worst seen at a British air show since the 1952 Farnborough crash when a de Havilland DH.110 fell into the crowd, killing 31 spectators.
The Civil Aviation Authority has since brought in new rules covering vintage aircraft flights, but these only relate to air displays.
This year's Shoreham Airshow has been cancelled out of respect for the families of the victims. A full inquest is expected to take place in June.
Sources: CAA, Sky, BBC, CNS, ABC
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