EUROPE'S aviation safety ­watchdog was told three years ago to recommend that all twin-engined helicopters used by emergency services be fitted with black box recorders, it has emerged.

The recommendation came after a fatal air ambulance crash in Hungary involving the same make and model as the one which crashed in Glasgow on Friday night, killing nine people.

Air accident investigators have begun their inquiry into what caused the police helicopter to suddenly drop out of the sky and crash through the roof of the Clutha Vaults pub at the weekend.

The pilot and two officers in the aircraft died, along with six people who were inside the bar at the time.

The probe has been complicated by the lack of a flight recorder - or 'black box' - which would have provided a precise account of events aboard the stricken helicopter in the minutes before it went down.

However, it has now emerged that recommendations were put to the European Aviation Safety Agency in 2010 calling for all Eurocopter EC 135 helicopters to be installed with flight data recorders following a fatal air ambulance crash in Hungary in July 2008 involving one of the aircraft which was carrying a two-year-old burns victim to hospital in Budapest.

The proposal was listed in EASA's 2010 Annual Safety Recommendations Review, when EASA stated that the call was "under consideration".

The text of the notice by Hungary's aviation safety authority said the EASA should "promote the safety benefits of fitting, as a minimum, an aircraft data recording system and a cockpit audio recording system to all twin-engine helicopters flying Category As missions".

However, it is unclear what happened next. EASA have yet to respond to The Herald's request for details.

It comes as the bodies of the nine people who died were being released to their families and preparations were being made for their funerals.

Pilot David Traill, 51, died alongside police constables Tony Collins, 43, and Kirsty Nelis, 36. The six people killed inside the pub have been named as friends Samuel McGhee, 56, and John McGarrigle, 57, from Glasgow, 48-year-old Gary Arthur from Paisley, Robert Jenkins, 61, and Mark O'Prey, 44, both from East Kilbride, and Colin Gibson, 33, from Ayr.

First Minister Alex Salmond told MSPs at Holyrood yesterday: "The procurator-fiscal has concluded his work to identify those who died, and authorised the release of their bodies to their families today. This will allow families, with the support and assistance of police family liaison officers, to make their funeral arrangements."

He also called for investigation into the crash to be carried out as quickly as possible and said a preliminary report by the Air Accidents Investigation Branch (AAIB) was expected within the next few days.

Eyewitnesses described ­hearing strange noises coming from the helicopter on Friday night, seconds before it plunged vertically into the roof of the Clutha, on the banks of the River Clyde, at 10.25pm.

No mayday call was issued beforehand by the pilot, according to the findings of the Air Accidents Investigation Branch.

In the 2008 crash in Hungary, the air ambulance was en route from Paks, 73 miles south of the capital, when it vanished from radar contact on the outskirts of Kiskunlachaza.

The pilot had attempted to make an emergency landing but the helicopter crashed and overturned, severely damaging the cabin and causing the tail section and skids to break off as it hit the ground.

The paramedic was killed on impact and the pilot died in hospital three days later from his injuries. Both the toddler and the toddler's mother suffered serious injuries, while the on-board doctor, who suffered minor injuries, was able to call for help.

Despite the fatal crashes in Glasgow and Hungary, the German-made Eurocopter EC 135 boasts al robust safety record and is widely used as an air ambulance and police helicopter in Europe, Canada, the United States and Japan.

An enhanced regime of safety checks was introduced last year by Bond Air Services - which owns and maintain the helicopters used by the police and ambulance services in Scotland - after manufacturer Eurocopter issued an alert about cracks found in the main rotar hub of a Eurocopter EC 135 in France.

Although Scotland's ­emergency EC 135s were given a clean bill of health, Bond agreed to carry out enhanced checks every 50 flying hours.

David Learmont, operations and safety editor for Flight Global, said: "It's probably one of the world's most modern and sophisticated twin-engine helicopters. It has an excellent safety record. I would love to have one myself.

"The bottom line is it didn't crash because it's an EC135 any more than car crashes are caused by a particular type of car. You wouldn't read about a crash on the motorway involving a Ford Focus and think 'well that's it, I'm definitely not buying one of those'.

"Unsafe aircraft are simply not allowed to fly. This helicopter didn't crash because it was unsafe."

In offshore helicopter ­ditchings involving Eurocopter's Super Puma model, investigators were able to retrieve black boxes to help unravel why the crashes occurred.