The pilot of a police helicopter that crashed into a pub and killed 10 people should have made an emergency call "long before" before the final stages of the flight, according to an expert.
Pilot David Traill, two crew members and seven customers in the Clutha bar in Glasgow were killed when the aircraft crashed on to the roof of the building on November 29 2013.
Marcus Cook, senior inspector at the Air Accidents Investigations Branch (AAIB), told a fatal accident inquiry (FAI) he would have expected an urgency and mayday alarm to have been raised due to low fuel levels but none were made.
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He confirmed there had been five low fuel alerts made to the crew during the flight and agreed ignoring such notices would be "downright dangerous".
Pilots are expected to land within 10 minutes of receiving a low fuel warning and no indication was given to air traffic control there were any issues with the flight.
Mr Cook said: "If he knows he will be landing with less than the final reserve he should make a mayday call.
"If he thinks it's going to be close to the final reserve he should make a pancall."
He added: "Speaking to other police helicopter pilots, they all say the one thing you always keep an eye on is how much fuel you have on board."
Sheriff Principal Craig Turnbull, sitting at a temporary court at Hampden Park, suggested Mr Traill should have made a mayday when at Bargeddie, to which the inspector replied: "If not before."
Mr Cook said: "One could suggest that a pancall may have been appropriate earlier on, if you had realised the chance of landing before low fuel reserve.
"Certainly long before the final stages of the flight."
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A 2015 report by the AAIB estimates the aircraft had around 100kg of fuel when it was carrying out a surveillance task at Bargeddie, at around 10.14pm.
It estimates 86kg of fuel was remaining when it reached Bothwell at 10.19pm, while it is expected to return to landing with at least 85kg.
It was heard the aircraft usually burns about 3kg of fuel every minute.
It was also heard there are no plans to reopen the AAIB investigation into the crash.
Phil Sleight, deputy chief inspector of air accidents, told the Clutha FAI there had been new documents presented but none of them were considered new or significant enough.
The purpose of the FAI is to determine the cause of the deaths, establish whether they could have been prevented and enable the sheriff to make recommendations that could prevent fatalities in similar circumstances.
More than 100 people were at the Clutha Vaults pub when the helicopter, returning to its base on the banks of the River Clyde , crashed through the roof.
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The 2015 AAIB report found two fuel supply switches were off and the pilot did not follow emergency procedures after a fuel warning in the cockpit.
The Crown Office has previously said there is insufficient evidence for criminal proceedings.
A total of 57 Crown witnesses are expected to give evidence at the inquiry, down from a previous estimate of 85.
Police have taken more than 2,000 statements as part of preparations for the FAI, while the Crown has around 1,400 productions.
The inquiry is expected to involve around three months of evidence spread over six calendar months this year.
The inquiry continues on Wednesday.
