A report into the cause of the Clutha helicopter crash which killed ten people is expected to leave many questions unanswered and lead to calls for the introduction of flight recorders on all passenger aircraft.
The long-awaited Air Accident Investigation Branch (AAIB) report into the tragedy on November 29 2013 is expected to be published today.
Relatives were given an advance briefing on its findings this week, and said the report makes a compelling case for black box flight recorders to be fitted in all passenger-carrying aircraft.
The 102-page report is expected to identify an issue with the position of the aircraft's fuel switches and that the engine had been "starved" of fuel.
More than 100 people were enjoying a night out at the Glasgow pub when a police helicopter returning to its base on the banks of the River Clyde crashed through the roof.
In an interim report published last year, the AAIB said both engines on the aircraft failed but the cause was not outlined.
The interim report said the engines had ''flamed out'' before the helicopter crashed at 10.22pm, killing the pilot and two police constables on board as well as seven people in the pub.
Speaking after a family briefing on Wednesday, Ian O'Prey, whose son Mark died in the bar, said: "The pilot wasn't at fault, that's for certain.
"There were switches left on, or off, and the engine had fuel starvation, that's basically it."
John McGarrigle, who lost his father, John, said: "Flight data recorders should be installed in every passenger-carrying aircraft - simple as. If we had that, we would know a lot more. It's just question upon question upon question.
He added: "I'm furious. I came here very optimistic, very hopeful, knowing that the AAIB are very impartial but I just feel really let down by those guys because these are the people that we came here tonight to get answers off of and we never got any answers.''
Anne-Marie Kennedy, who was working behind the bar and was trapped in the wreckage, said: "It's shown me that they should have black boxes for defo, it's shown me the need for other regulation, but other than that nothing."
Those who were in the helicopter - pilot David Traill, who was attached to Police Scotland's air support unit, and police constables Tony Collins and Kirsty Nelis - were killed when the helicopter crashed into the building.
As well as Mr O'Prey and Mr McGarrigle, those inside the pub who were killed were Gary Arthur, Colin Gibson, Robert Jenkins, Samuel McGhee and Joe Cusker.
Jim Morris, partner at Irwin Mitchell solicitors and an expert in aviation law, said the investigation had been impeded by the lack of a black box flight recorder.