The Shoreham fighter jet that killed 11 people after crashing during an airshow may not have had legal clearance to fly before the tragedy, an interim report has found.
The vintage Hawker Hunter jet flown by pilot Andrew Hill failed to pull out of a loop-the-loop and crashed on the A27, plummeting into motorists and spectators.
It has now been revealed the jet may not have had the proper licence to fly for eight months before the disaster on August 22.
An interim report released by the Air Accidents Investigation Branch yesterday found the organization in charge of the 60-year-old jet's maintenance only had permission to keep it in operation until December 2014.
A request to fly the jet in 2015 was submitted in January 2014 but had not been approved by the Civil Aviation Authority (CAA) before its doomed flight at Shoreham Airshow.
To gain permission to fly the maintenance organization was required to submit an Alternative Means of Compliance - a proposed program of work on the engine.
But the organization received an email from the CAA at the end of January asking for "additional information" to be included in the formal submission.
The organization claimed it had "no recollection or record" of the CAA response and the investigation found no formal proposal was made to the CAA to ensure that the jet had clearance to fly after December 2014.
The organization asked for an update in April 2014 on its January proposal but investigators have not been able to identify any response from the CAA.
The report said: "The CAA . . . could not determine if the aircraft met the requirements of its Permit to Fly from December 2014 onwards."
The CAA said that it is "trying to clarify the position".
Emergency workers had to delay their response to the crash because of the risk posed by out of date and damaged explosive cartridges in the ejector seat, the report also found.
The report said the seats were a "significant hazard" that delayed rescue teams until they were made safe.
Air investigators said the manufacturer support for the jet ended after it was retired from military service and its technical manual had not been updated.
Mr Hill, 51, who survived the jet crash, was finally interviewed over the disaster after long-winded delays as police tried to establish his fitness for interview.
It is not clear whether the experienced pilot ejected himself from the plane or was thrown free.
An initial interim report concluded there were "no abnormal indications" during the flight.
The aircraft was owned by Graham Peacock, a businessman based in Essex, who bought it for £65,000 in 2012.
At the time of purchase it had a Fatigue Index of 30 out of 100, meaning it still had 70 per cent of its total lifespan left.
Its engine had been flown for 351 hours, also a low number, with another 100 hours of flying time before an overhaul was needed.
A final accident report is still to be published.
Hawker Hunter (G-BXFI), crashed onto public road during air display, near Shoreham Airport, 22 August 2015 - investigation update.
The aircraft was taking part in an air display at Shoreham Airport during which it conducted a manoeuvre with both a vertical and rolling component, at the apex of which it was inverted. Following the subsequent descent, the aircraft did not achieve level flight before it struck the westbound carriageway of the A27.
Special Bulletin S3/2015 was published on 4 September 2015 to provide preliminary information about the accident gathered from ground inspection, radar data, recorded images and other sources.
This Special Bulletin is published to highlight findings of the AAIB investigation regarding ejection seat safety and the maintenance of ex-military jet aircraft, and to assist the Civil Aviation Authority in its ‘Review of UK Civil Air Displays’ announced on 9 September 2015. A final report will be published in due course.
Seven Safety Recommendations are made.