A preliminary US intelligence assessment has indicated the aircraft was likely shot down by an early version of the Russian-built Buk missile system known as the SA-11 or "Gadfly".

Bob McGilvray, an Australian who served in the British Army for 12 years and was based in Germany during the Cold War, said it would have been an "easy hit".

"The Buk would have made utter breakfast of the airliner because of the size of it," Mr McGilvray, a retired captain, said.

"The operators would have been in no doubt that it was an airliner as well, because that was an air route that was used every day by 100 aircraft.

"They would have been able to watch the aircraft for probably about five minutes at least before they fired the missile, so they would have had plenty of time to work out what it was."

Buk is a sophisticated vehicle-mounted system which includes a separate surveillance radar vehicle, called the Target Acquisition Radar.

The TAR gives information about targets to a control vehicle, which in turn feeds information to separate missile launcher vehicles known as Transporter Erector Launchers.

The system is built for targeting medium altitude aircraft and can seek and blow up targets at up to 72,000 feet, meaning it could easily destroy the MH17 at 33,000 feet.

The missiles, which have their own radars to detect when they are approaching a target, explode the warhead below or sometimes above the aircraft.

The warhead contains explosives and is wrapped in steel bars. The explosives damage the aircraft but it is the steel bars flying out that "tear the aircraft to pieces", Mr McGilvray said.

But RMIT aerospace engineering academic, Reece Clothier, said the Buk system did not have the technology to determine if it the plane was military or civilian.

“The Buk system is radar guided but at the end of the day the missile doesn't know the difference between a military and a civil aircraft, more advanced systems do," Dr Clothier said.

Robert Pape, an expert in international security affairs at the University of Chicago, said the SA-11 travels at close to 5000km/h.

‘‘They are designed to shoot down fighter jets that are going twice the speed of sound,’’ he said.

‘‘To shoot down a commercial airliner lumbering at 600 miles an hour (1000km) and can’t move is a piece of cake.’’

The type of surface-to-air missile used could have pierced the plane with shrapnel after exploding close to it, said Bill Waldock, a professor of safety science at Embry-Riddle Aeronautical University, in a telephone interview.

It appears from public reports that the plane was struck toward its tail, blowing most of the structure away, Professor Waldock said.

‘‘That thing uses a proximity fuse which goes off when it gets close,’’ Waldock said.

‘‘The warhead is like a giant shotgun shell sending multiple shards of metal through the plane. It’s doubtful it hit the plane, but once you lose the tail you can’t fly the plane,’’ he said.

with Bloomberg