As the MH17 investigation ramps up, Prime Minister Tony Abbott is concerned that all bodies may not be recovered from the wreckage.

Crucial black box data from flight MH17 will be analysed within days, as officials begin identifying the Australian victims of the disaster and prepare their remains for the return home.

But Prime Minister Tony Abbott fears not all the Australian’s remains may be recovered unless there’s greater co-operation from pro-Russian separatists in control of the crash area in eastern Ukraine.

The Malaysia Airlines’ flight recorders will be examined by Britain’s Air Accidents Investigation Branch (AAIB), which will extract the data and send it to Dutch and Ukrainian experts for analysis.

With the extraction expected to take no longer than 24 hours, Dutch authorities leading the investigation will then decide what information will be made public about the fate of the Boeing 777 carrying 298 passengers and crew.

Mr Abbott is seeking advice on how best to cordon the 50sqkm crash zone and enforce a UN Security Council resolution that insists on “dignified, respectful and professional” treatment of the human remains.

“It is quite possible that many bodies are still out there in the open in the European summer subject to interference and subject to the ravages of heat and animals,” Mr Abbott said.

Australia’s special envoy to Ukraine, Angus Houston, led a ramp ceremony on Wednesday night to farewell the remains of up to 200 people being transported by Australian and Dutch military aircraft from Kharkiv in Ukraine’s northeast to the Netherlands.

Mr Houston described the downing of MH17 as “a tragedy of unspeakable proportions” at the ceremony, before a minute’s silence was observed.

The remains will be received at Eindhoven Airport by officials including Australia’s Governor-General Sir Peter Cosgrove.

A train carrying the remains of victims recovered from the plane, downed in the Donetsk region, reached the safe territory of Kharkiv – Ukraine’s second-biggest city – on Tuesday night.

Mr Houston, a former defence force chief, said he hoped to have Australian team members at the crash zone “in the near future”, despite extensive fighting in the area.

Up to 39 Australian citizens and residents were among those killed when MH17 exploded over eastern Ukraine on July 17.

Australian officials are confident the airliner was brought down by a ground-fired missile.

“We have been of the view for some time, we know how this occurred and there will be more evidence to back that conclusion,” Foreign Minister Julie Bishop said.

“But we need to determine who is responsible.”

Ms Bishop has received international plaudits for lobbying the UN Security Council – including the Russians – to unanimously adopt a resolution demanding international access to the site.

Former US president Bill Clinton told an AIDS conference in Melbourne on Wednesday he was “proud” to have been in Australia when Ms Bishop achieved her aim.

Mr Clinton also urged world leaders to keep up pressure on Russia to reveal what it knew about the attack, after reports it might have been a mistake by separatists.

“I hope that all of our countries who value freedom and honour (won’t) give in to the temptation to say: ‘Well, maybe we should weaken our resolve to take a strong stand because after all they didn’t mean to shoot this plane down’.”

The federal government has offered to cover the cost of victims’ families to travel to the Netherlands.

Separatists handed over the two black boxes to Malaysian authorities on Monday.