The Ministry of Defence has renewed its attack on the dead pilots of Chinook ZD576, after the publication of documents that revealed a "dangerous" flaw in software installed on the type of helicopter that crashed.
The newly-disclosed documents add to evidence that the Chinook Mk2 was not airworthy in June 1994 when Chinook ZD576 crashed on the Mull of Kintyre, killing all 29 on board, including 25 senior police and intelligence officers.
Senior officers found the two pilots Flight Lieutenants Jonathan Tapper and Rick Cook grossly negligent, although an RAF Board of Inquiry did not rule out a Fadec computer problem as a contributory factor.
Now Stephen Dalton, chief of the air staff, has written a response to media coverage of the new evidence.
He says: "We have always made clear that we would revisit the findings if new evidence was presented. Despite the efforts over many years of those campaigning to clear the pilots, including an exhaustive report submitted in 2008, no such evidence has ever been found.
"The computer software issues raised in the documents obtained by the BBC were well known at the time and had been factored into the operating instructions. These issues were discounted in the context of this accident following a thorough independent assessment by the Air Accident Investigation Branch.
"This led the Board of Inquiry to conclude - along with those who have repeatedly reconsidered this over the years - that there was no evidence of technical failure which would have been a factor in the crash. What was exposed, in a diligent and logical analysis, was that the pilots consciously breached their operating rules, thereby knowingly placing their aircraft, passengers, crew and themselves at risk.
"This was the basis for the gross negligence finding. The Chinook helicopter has a remarkable safety record and has proved a mainstay of recent operations. Aircraft losses are not always due to equipment failings and it is a disservice to our people, particularly those working heroically daily in Afghanistan, to see a conspiracy behind every tragic loss."