Report expected to clear Chinook pilots of blame
The Mull of Kintyre crash, just months before the IRA's 1994 ceasefire, was the RAF's worst peacetime accident.
The Chinook carrying 25 senior intelligence officers and four crew was piloted by Flt Lt Jonathan Tapper and Flt Lt Richard Cook.
On 2 June 1994 the flight took off from RAF Aldergrove and was on its way to Fort George in Inverness where those on board were due to attend a security conference.
As it approached the Scottish coast the aircraft begin to climb over the Mull of Kintyre, but then crashed into the hillside.
Alan McQuillan, a former RUC assistant chief constable, said: "These were some of the most experienced and capable people in the intelligence field in the UK, if not the world.
"These were guys that were working for 20 to 30 years and it was just a huge gap to try to replace them."
The cause of the 1994 Chinook crash has been a vexed question.
The original RAF Board of Inquiry came to no conclusion, nor did the fatal accident inquiry shortly after the crash.
But then two air marshals, Sir William Wratten and Sir John Day, accused the two pilots of "gross negligence".
They accused the pilots, both of whom were trained by special forces, of flying too fast and too low in thick fog.
That judgement has long been challenged both by the pilots' families and the relatives of some of those who died on the flight.
A new review, chaired by retired judge, Lord Philip, for the Defence Secretary, Liam Fox, is expected to clear the pilots of blame.
But Sir Michael Graydon, a retired air marshal, disputes the findings of the new inquiry.
He said: "It was a terrible accident. Do you think the RAF would have blamed its pilots if there was any other reason other than air crew error? Absolutely not."
There have been a number of questions raised in recent years about the air-worthiness of the Chinook, especially about the helicopter's software, Fadec.
It controlled the Chinook's power, speed and steering.
Dr Susan Phoenix, whose husband Ian, a senior RUC officer, died in the crash, believes there has been a cover-up.
She said she is delighted that the pilots are about to be cleared because the case against them can not be proved beyond reasonable doubt.
"This Chinook didn't have an air-worthiness certificate and I personally only discovered that last year. Its release to service wasn't properly signed," she said.
Another widow, Ann Magee whose husband Kevin, a detective inspector, had spent 17 years in the RUC Special Branch, said she remembers being shocked when she was told at the time that the pilots would be blamed.
She is glad for the families of the pilots that the men are about to be cleared.
"I think they will feel the physical loss of the burden on their shoulders that they have carried for so long. It will be wonderful," she said.
Senior RUC officers at the time of the crash have told the BBC that neither they nor the families ever blamed the pilots for what happened.