Image copyright PA Image caption The Hawker Hunter jet plummeted on to the A27 in August last year

Organisers of the Shoreham air show, where a jet crashed last year killing 11 people, were unaware of the pilot's display plans, an interim report says.

The Air Accidents Investigation Branch (AAIB) also said they failed to carry out a proper risk assessment.

The vintage jet fell to the ground on a busy road during a rolling manoeuvre, destroying a number of vehicles and bursting into flames.

Andy Hill, pilot of the 1959 Hawker Hunter, survived.

The Shoreham air show organisers said in a statement that the report "reflects our assertions that we, as the flying display organisers, complied with the existing Civil Aviation Authority (CAA) CAP 403 regulations".

They added: "We are confident that we made every effort to follow the CAA's guidance."

Congested areas

According to the AAIB, the flying display director at Shoreham was well qualified, but he was not fully aware of the sequence of display manoeuvres the pilot of the jet was planning to carry out.

He was not, therefore, able to identify where they would take place, or which groups of people would be put at risk.

Media playback is unsupported on your device Media caption "To know that [the pilot] didn't discuss what he was going to be doing... really, really shocked me" - Giovanna Chirico, fiancée of crash victim Mark Trussler

The report notes that in a previous display, in 2014, the same aircraft had flown over residential areas several times, as well as performing a steep turn over the town centre of Lancing.

This was despite its flying permit specifically stating that it should not be flown over congested areas and the show's organisers operating under similar constraints. However, the pilot was not told to stop his display.

Analysis: Richard Westcott, BBC transport correspondent

This report doesn't tell you why the Shoreham jet crashed. That final report won't be out for some weeks yet.

But it will have big implications for air shows up and down the country. It'll mean tougher rules, more red tape, higher costs, better safety and it could also spell the end for dozens of the smaller shows.

Some have already cancelled because of the uncertainty and because of higher fees being brought in by the regulator.

The CAA says the extra cash will pay for more staff to improve safety. Show organisers disagree, saying it's more of a money-making exercise. Both sides maintain that safety is their number one priority.

More than six million people go to air shows every year, making it the second-biggest spectator event after football.

Air show safety tightened after Shoreham

CAA says air shows must adopt safety measures

Similar breaches

According to the report, investigations have shown that this was not an isolated incident. Similar breaches have taken place at Shoreham and at other venues, involving other aircraft and pilots.

The AAIB is also critical of the way crowds outside the airfield were handled, including at the junction of the A27 where the accident occurred.

This was a site where crowds had been known to gather in large numbers in previous years, and the AAIB says stewards had been employed to ask people to move on.

However, it adds that: "Neither the organisers nor the police had requested or been granted the legal power to prevent people from being in this area and their efforts did not prevent gathering on the A27 junction."

Image copyright Zak Hussein Image caption Pilot Andy Hill was interviewed by police in December

Pilot permits

Further criticism was aimed at the process under which pilots gain their display permits, which allow them to qualify using one aircraft model, then use a variety of others in the displays themselves.

This was the case with the pilot of the Hawker Hunter, who had qualified using a different type of aircraft from the one he was piloting in the show.

The AAIB also notes that the pilot, Andy Hill, had been prevented from completing a display at a different venue in 2014 because the display director had been concerned about one of his manoeuvres.

No action was taken on that occasion beyond an informal discussion with Mr Hill.

The victims:

Image copyright BBC/Sussex Police/Facebook Image caption (Top row, left to right) Matt Jones, Matthew Grimstone, Jacob Schilt, Maurice Abrahams, Richard Smith. (Bottom row, left to right) Mark Reeves, Tony Brightwell, Mark Trussler, Daniele Polito, Dylan Archer, Graham Mallinson

Matt Jones, a 24-year-old personal trainer

Matthew Grimstone, 23, a Worthing United footballer who worked as a groundsman at Brighton & Hove Albion

Jacob Schilt, also 23 and also a Worthing United player, was travelling to a match with Mr Grimstone

Maurice Abrahams, 76, from Brighton, was a chauffeur on his way to pick up a bride on her wedding day

Friends Richard Smith, 26, and Dylan Archer, 42, who were going for a bike ride on the South Downs

Mark Reeves, 53, had ridden his motorcycle to the perimeter of Shoreham Airport to take photos of the planes

Tony Brightwell, 53, from Hove was an aircraft enthusiast and had learnt to fly at Shoreham airfield

Mark Trussler, 54, is thought to have been riding his motorcycle on the A27

Daniele Polito was travelling in the same car as Mr Jones

Graham Mallinson, 72, from Newick, was a keen photographer and retired engineer

The Civil Aviation Authority (CAA) is responsible for allowing air shows to go ahead and monitoring their safety.

But according to the report, last year its representatives only attended 18 of the 254 displays it authorised. In the United States, the regulator attends every show.

The AAIB has issued a series of recommendations which are designed to make air shows safer in future.

In total, the report sets out 14 recommendations affecting the way shows are organised and regulated, and how pilots are qualified to take part in them.

The AAIB says the CAA should "introduce a process to immediately suspend the Display Authorisation of a pilot whose competence is in doubt, pending investigation of the occurrence".

Responding to the latest report a CAA spokesperson said: "We will now review the AAIB's bulletin in detail and consider all of its recommendations carefully. We will also factor the AAIB's findings into our ongoing review of air display safety, which we expect to complete in the coming weeks."