The crew's captain was sick on the day of the crash
Ten airmen who perished when their Washington bomber mysteriously crashed while on a training exercise are to be commemorated 55 years on.
The cause of the crash near Llanarmon-yn-Ial in Denbighshire which led to one of the largest RAF death tolls in peacetime has never been established.
A church service is to be held in September and a slate memorial erected.
Two retired North Wales Police officers are trying to find relatives of those who died so they can attend.
Ross Duffield, who was a detective chief superintendent, described the air crash on 8 January 1953 as a real mystery.
The Washington bomber has taken off on a routine training flight for the members of 90 Squadron from RAF Marham in Norfolk.
LOST CREW OF THE B29 WASHINGTON BOMBER
Squadron Leader WR Sloane, 32, from Belfast
Pilot Officer CB Speller, 28, from Finsbury, London
Pilot Officer MJ Lightowlers, 21, Leeds
Sgt EF Wheeler, 18, Hemel Hempstead
Sgt KA Reakes, 28, Cardiff
Sgt RFS Anderson, 24, Edinburgh
Sgt ED Pearton, 28, Newport, south east Wales
Sgt AS Martin, 22, Kent
Sgt MJ Clifton, 18, Cambridge
Sgt RG Hughson, 18, Edinburgh
The plane flew over the North Sea and back across northern England, with the last radar contact over the Wirral at about 13,000ft.
"It went into a steep dive and no-one knew why, " explained Mr Duffield.
One witness reported that the engine appeared to rev up then died.
The plane's tail broke away and landed upside down in woods at Gelli Gynnan Farm.
People rushed to help and three went inside the burning aircraft which later exploded, but no-one survived.
A board of inquiry failed to uncover the reason for the crash.
"Clearly something went dramatically wrong with the engine. The rear tail section fell off and it plunged out of the sky," Mr Duffield added.
He and former police sergeant Darryl Jones started investigating after he spotted six of the airmen's graves at Hawarden cemetery.
Six of the crew are buried at Hawarden cemetery in Flintshire
"I just thought it was so strange," he said.
The pair trawled through newspaper cutings, the web and research from the local conservation society to find out more.
"It just snowballed. It started off as a bit of research for interest's sake and it took on a life of its own."
The memorial service will take place at Llanarmon-yn-Ial church on 6 September.
Bearers from RAF Associations, the Air Training Corps and Royal British Legion in north Wales will parade their standards into the church, and there will be a representation from RAF Marham, from where the Washington first flew.
Relatives of four of the airmen will attend the memorial.
Among them will be the daughter and son of Squadron Leader Bill Sloane, the captain of the plane, who was from Belfast.
Alex Hughson, the brother of Sgt Bobby Hughson, one of the airgunners, is flying from California with his wife Lyn.
Nick Clifton, a nephew of Sgt Maurice Clifton, another airgunner from Cambridge, and other members of his family from Cambridgeshire will also attend.
Wendy Chilcott, from Weston-super-Mare, a niece of Sgt Ken Reakes, who came from Cardiff, will also attend.
But Mr Duffield said they were still anxious to contact others for what was a historical moment in their families' lives.
"There were another six aircrew on the aircraft and despite me sending letters to regional newspapers in their home towns, I have been unable to contact any more relatives," Mr Duffield said.