Eyewitnesses have described hearing noises coming from a police helicopter before it crashed into the Clutha pub.
The final seconds of the flight in Glasgow city centre on 29 November 2013 were described at the opening day of a hearing into the tragedy.
Statements on behalf of six of the 10 victims were also read out after a minute's silence was observed.
The Fatal Accident Inquiry heard from a number of people, including a taxi driver and pedestrians.
Pilot David Traill, 51; PC Tony Collins, 43; and PC Kirsty Nelis, 36, lost their lives along with seven customers who were in the bar on Stockwell Street.
They were Gary Arthur, 48; Joe Cusker, 59; Colin Gibson, 33; Robert Jenkins, 61; John McGarrigle, 58; Samuel McGhee, 56; and Mark O'Prey, 44.
In his evidence, Ernest Docherty, 64, told the inquiry - which is being held in a temporary court at Hampden Park football ground - that the Police Scotland helicopter "was like an old car trying to start but a thousand times louder".
The retired transport worker said the noise grew louder as it flew overhead, causing him to hunch in the street.
Andrew Bergen, 30, was walking along the river bank when he saw the helicopter flying normally.
The solicitor added: "It made what I can only describe as a spluttering noise."
Mr Bergen said the helicopter's tail dipped and pointed toward the ground.
He went on: "Simultaneously the lights went out and it seemed to me that the rotor stopped spinning. It was still turning but not under power."
Taxi driver Tariq Malik, 41, was having a cigarette in the car park of the Grand Mosque on the opposite side of the river Clyde, when he spotted the helicopter.
He recalled it was a clear night and everything initially seemed normal until it suddenly lost power.
He told the court: "All I could hear was a swooshing sound as it fell through the sky."
Christopher Jarvie, 36, described a "stuttering noise" while Brian Stewart, 50, said the sound from the helicopter was similar to a car stalling. Another witness, Craig Welsh, 42, talked of hearing a "whining sound and then there were two distinct thuds".
Earlier, statements from six of the families of those killed were read out by their legal representatives.
Testimonies came from the families of Mr McGhee, Mr Arthur, Mr Jenkins, Mr Gibson, Mr McGarrigle and Mr O'Prey.
No statement was provided by relatives of Mr Cusker or the pilot and his two crew.
Mr McGhee's daughter Kerry told how her father was born and bred in Castlemilk. The bus driver had to take early retirement to care for his partner, who died of cancer in 2007.
She wrote: "He was a good friend, neighbour and a sad loss to our close-knit community."
Colin Gibson was celebrating a friend's birthday on the night of the tragedy. He had never been in the bar before.
In a statement, his family said: "We will never know what he would have went on to achieve. He just happened to be in the wrong place at the wrong time."
Mark O'Prey's father, Ian, said his "wonderful son" had "many virtues" and "loved life and lived it to the full".
He thanked the hearing for the minute's silence, but said added: "After five and a half years of silence from the Crown Office it is of no consequence to me personally."
'A loveable rogue'
Mary Kavanagh's partner, 61-year-old Robert Jenkins, was the oldest to die.
Donald Findlay QC read out a statement on behalf of Ms Kavanagh, which said the father-of-two had many friends and was a keen football fan who would have loved to work at the Scottish Football Museum, based at Hampden Park.
He said: "Mary finds it very ironic that the FAI is taking place at a venue that Robert held in such high esteem."
The couple were in The Clutha on the night of the disaster. She last saw Mr Jenkins as he went to the bar to buy her a cranberry juice.
Mr Findlay concluded: "All Mary wants to know is why she went into the bar with the man she was going to spend the rest of her life with and came out alone."
The sisters of Gary Arthur described him as a "joker" and a "loveable rogue", and said the disaster had robbed him of so much.
Their statement concluded: "Nothing will ever bring our brother back, but hopefully we will be given the chance to have closure over the last five years and remember Gary as a much loved person and not just a victim from The Clutha."
John McGarrigle's son, John, described his father as his "hero". The court heard he was a writer and a Clutha regular who always used to sit in the same seat.
The statement said: "His talent was immense and his take on things was wry and humorous."
More than 100 people were in the bar when the Police Scotland helicopter crashed through the roof at 22:22. As well as the 10 who died, 31 people were injured.
The Eurocopter EC 135, operated by Bond Air Services, had been returning to its base on the banks of the River Clyde.
The inquiry will not sit every day and is expected to hear about three months' worth of evidence between now and August.
The first four weeks will involve eyewitnesses and representatives of the the Air Accidents Investigation Branch (AAIB) and Airbus.
In October 2015 a report from the AAIB concluded the pilot did not follow emergency protocol and flew on despite low fuel warnings.
It also found fuel transfer pumps were turned off and a controlled landing was not achieved for "unknown reasons".
And it recommended all police helicopters be equipped with black box flight recording equipment.
- 29 November 2013: Police helicopter crashes on Clutha bar in Glasgow, killing 10 people.
- 9 December 2013: AAIB preliminary report finds there was 95 litres of fuel onboard the aircraft.
- 14 February 2014: AAIB special report finds both engines "flamed out". One of the fuel tanks was empty, while a second contained 0.4 litres. A third contained 75 litres, but transfer pumps to take this fuel to the other two engine tanks were switched off.
- 23 October 2015: AAIB final report finds main cause of accident to be mismanagement of the fuel system by the pilot.
- 24 November 2017: Fatal accident inquiry announced.