The police investigation into the plane crash at the Shoreham Airshow - which killed 11 people - is being delayed as detectives are being forced to seek permission from the courts to gain access to key information from the Air Accidents Investigation Branch (AAIB), a pre-inquest review has heard.
Detective Chief Inspector Paul Rymarz, of Sussex Police, told the hearing that officers had applied to the High Court for access to "protected material" held by the AAIB including cockpit recorders and footage, witness accounts, expert reports and documentation.
He said: "There has been a significant delay in obtaining some material in this case because of the legislation that governs the investigation of such incidents."
Mr Rymarz said "very good liaison" existed with the AAIB which had "sought to co-operate to the maximum extent possible under the regulations".
He added: "However, police have had to work without the specialist knowledge and assistance of AAIB and instead used the AAIB reports released thus far to inform the investigation.
"Until the relevant court makes a ruling with regards to this material, the police investigation cannot progress effectively, as without it, key evidence is missing and experts are not in a position to provide interpretations."
Mr Rymarz said police had taken 330 statements, 3,500 documents and obtained images or video from more than 200 members of the public as part of the investigation.
Penelope Schofield, senior coroner for West Sussex, proposed for the full inquest to be held in March 2017 to last an estimated eight weeks.
She said the inquest might have to be adjourned in the case of a prosecution but she would be "reluctant" to do so if the charge was a "minor" one.
Ms Schofield said: "If it's a particular type of offence I will be required by the CPS to adjourn the inquest pending the criminal prosecution. If it's a lesser offence, then clearly that's a consideration for a further review.
"I am aware that a criminal case could take some time and that would add a further delay to the families having some closure."
More than 100 people, including family members and legal representatives for the next-of-kin, show organisers, insurance companies and investigators, attended the hearing at Horsham which was held for administrative reasons to organise the inquest, which will be the largest ever held in West Sussex.
The pilot of the Hawker Hunter, Andrew Hill, 51, from Hertfordshire, was not present at the hearing.
His plane crashed into spectators watching from the A27 at the perimeter of the site in one of Britain's worst airshow disasters. He was thrown clear from the 1955 fighter-bomber and suffered life-threatening injuries but was discharged from hospital in September.
Mr Hill was voluntarily interviewed under caution by police in connection with the accident.
A spokesman for the AAIB told the hearing it had released three special bulletins into the crash on August 22 last year with its full report due to be released at the end of the summer.
Its most recent bulletin revealed that the airshow's risk assessment did not "show the range of hazards presented by different display aircraft."
Ms Schofield adjourned the proceedings for a further pre-inquest review hearing to be held on September 19.
This year's event has been cancelled out of respect for those affected.
Steps taken in the immediate aftermath of the disaster - such as banning ex-military jets from performing aerobatics over land - remain in place until the publication of a full air accident report into what caused the crash.
The Civil Aviation Authority has warned that a number of air shows will not go ahead this year unless they adopt new safety measures.
James Healy-Pratt, of Stewarts Law, who is representing six of the families, said outside the hearing: "The families deserve the truth about how their loved ones lost their lives in this accident.
"This inquest process is all about that and it is their best chance of getting to the truth.
"The families also want to make sure that further innocent lives are not lost at future air shows and this inquest process may well highlight further steps that are needed to be taken by the authorities and regulators."
He added: "If there are what I would call serious criminal charges brought by the CPS, it's likely the inquest will not take place until that serious criminal charge process has been completed.
"The worst case would be 2018; in my view, best case is this time next year, but it's factors outside the families' control. I have warned the families it could be a long time."
Jim Morris, of Irwin Mitchell, who is representing several families, said after the hearing: "This is likely to be a lengthy and complicated inquest and, crucially, it gives families the opportunity to put questions themselves or through their legal representatives to key witnesses involved in the tragedy and the investigation.
"We hope the inquest process will pull all relevant evidence together and provide a complete and detailed picture of the full chain of events that led to this terrible disaster.
"We have heard from the AAIB's recent Special Bulletin how the safety of air shows can be improved. The recommendations are welcomed but it is a matter of deep regret that it has taken the terrible loss of life at Shoreham before these recommendations, many of which are common sense, have been made."