http://news.bbc.co.uk/1/hi/uk/7398039.stm
The explosion which downed a spy plane in Afghanistan killing 14 servicemen on board was due to a "fundamental design fault" an inquest has heard.
The coroner had before heard it was because fuel leaked into a dry bay and ignited on contact with a hot air pipe.
But on Tuesday, a senior RAF officer said a mistake was made during a hazard assessment of the Nimrod which could have identified that risk.
It exploded minutes after refuelling in Afghanistan in September 2006.
Hindsight on hazard
Air Commodore George Baber told the inquest at Oxford Coroners Court that had they known then what they knew now, the Nimrod would not have been passed as safe to fly.
He led an Integrated Project Team (IPT), who with BAE systems carried out a comprehensive hazard analysis of the plane.
When hazards were identified and categorised at a meeting in August 2004, he said, the possibility of an explosion in the dry bay was graded in as "improbable".
It should have been graded higher and warranted further action, he admitted.
The design flaw was to have fuel in the same compartment as a hot air pipe, he said.
He told the inquest: "At the heart of this was a fundamental design flaw. This hazard assessment process was an opportunity to catch any inherent design flaw.
"We failed to catch that design flaw. The consequences were catastrophic and that is why we are here today."
He described the categorising mistake as a "failure".
Buck stopped
Asked by Michael Rawlinson, the lawyer representing the families of the dead servicemen, whether the Nimrod was safe to fly, Air Commodore Baber answered: "I find it difficult to answer because the simple answer is 'no' because we had an accident.
"Any aircraft we fly carry hazards all the time. Clearly if we knew then what we know now we would not have flown the aircraft."
As head of the IPT, he said he was responsible for deciding whether the aircraft was airworthy and the buck stopped with him.
The men died when a 37-year-old Nimrod exploded after undergoing air-to-air refuelling near Kandahar on September 2, 2006.
The crew on Nimrod XV230 had no means of tackling the initial fire and were forced to attempt an emergency descent to the air base. But it exploded into flames at 3,000ft.
Plane grounded
Earlier, the coroner heard how a technical problem grounded an RAF Nimrod plane due to be shown as part of the inquest.
Relatives were to view the plane but a hydraulic problem meant a second plane had to be shown at RAF Brize Norton, Oxfordshire, last week.