Malaysia Airlines flight MH17 may have been shot down "by mistake" by ill-trained pro-Russian separatists, US intelligence officials said tonight.
They dismissed Russia's accounts of the incident.
Evidence gathered so far suggests separatists launched the SA-11 surface-to-air missile that blew up the Malaysian airliner, but it remains unclear "who pulled the trigger" and why, said a senior intelligence official who spoke on condition of anonymity.
"The most plausible explanation... was that it was a mistake," and that the missile was fired by "an ill-trained crew" using a system that requires some skill and training, the official said.
The intelligence official cited previous incidents over the years in which both Russian and US forces have mistakenly shot down civilian airliners.
A Korean airliner was downed by a Soviet fighter jet in 1983 and US naval forces mistakenly shot down an Iranian civilian passenger plane in 1988.
"We've all seen mistakes in the past," the official told reporters.
Russian operatives have been spotted on the ground in eastern Ukraine but the US intelligence community had no explicit proof that Russians were with the SA-11 unit that fired on the airliner, officials said.
US satellite and other "technical" intelligence confirmed the airliner with 298 people on board was hit by an SA-11 surface-to-air missile from an area controlled by the pro-Russian rebels.
Although the United States had observed a flow of heavy weapons, including air defence systems, into Ukraine from Russia, intelligence agencies had not seen the larger SA-11 missiles being moved into the country before the airliner was downed, officials said.
The Russian military had been training the rebels at a large base in Rostov on various weapons, including air defence systems.
But US officials said there was no explicit evidence of the Russians training the separatists on the SA-11 missile batteries.
The senior intelligence officials said they chose to brief reporters partly to counter what they called misleading propaganda from Russia and its state-controlled media over the incident.
Allegations that the Malaysian Boeing 777 took evasive action in the air, similar to how a military plane might manoeuvre, had no basis and the reports amounted to "a classic case of blaming the victims," the senior official said.
The claim that the Ukrainian government had shot down the plane was not realistic, as it had no such missile systems in that area, which is clearly under the control of the rebels.
That scenario would mean Ukrainian government troops would have had to fight their way into the area, fire at the passenger plane and fight their way out again, the official said.
"That is not a plausible scenario to me," the official said.
Meanwhile, Malaysian officials have handed over the black boxes from flight MH17 to Dutch lead investigators of the crash in rebel-held Ukraine, the Netherlands government said tonight.
"The black boxes from flight MH17 have been handed over by Malaysian experts to the Dutch Safety Board (OVV) that is leading the international investigation," the foreign ministry said in a statement.
The black box data recorders will be sent to Farnborough in Britain for the data to be downloaded.
"Experts from several countries, including the OVV, will travel with the black boxes to Farnborough to help with the investigation," the ministry said.
The black boxes, which record aircraft systems data and cockpit voices, could prove crucial to the probe into the crash and will be brought to Britain by a Belgian military aircraft.
Exceptionally, the Dutch are in charge of the investigation, because the government in Ukraine does not have authority over the rebel-held crash site.
Separatists yesterday handed over the black boxes to Malaysian authorities, who brought them to Kiev.
Meanwhile, Malaysian officials have handed over the black boxes from flight MH17 to Dutch lead investigators of the crash in rebel-held Ukraine, the Netherlands government said tonight.
"The black boxes from flight MH17 have been handed over by Malaysian experts to the Dutch Safety Board (OVV) that is leading the international investigation," the foreign ministry said in a statement.
The black box data recorders will be sent to Farnborough in Britain for the data to be downloaded.
"Experts from several countries, including the OVV, will travel with the black boxes to Farnborough to help with the investigation," the ministry said.
The black boxes, which record aircraft systems data and cockpit voices, could prove crucial to the probe into the crash and will be brought to Britain by a Belgian military aircraft.
Exceptionally, the Dutch are in charge of the investigation, because the government in Ukraine does not have authority over the rebel-held crash site.
Separatists yesterday handed over the black boxes to Malaysian authorities, who brought them to Kiev.