Almost 300 passengers on board Malaysia Airlines flight MH17 were killed when it was shot down over Ukraine in July 2014.
The US and Kiev have pointed the finger of blame at separatist fighters and their Russian backers, although nothing has ever been proven.
The disaster will be explored on BBC Two tonight, when the documentary series, The Conspiracy Files, attempts to "sort the fact from the fiction". It will examine eyewitness testimonies, satellite photographs, wire taps, clandestine videos and expert evidence.
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Who Shot Down MH17? will also analyse the role of the Kremlin "in a world where the information war fought online can be just as significant as battles on the ground", says the BBC.
According to the official investigators, the Dutch Safety Board, the impact pattern and paint found on metal fragments proved the aircraft had been struck by a Russian-made 9M38 Buk surface-to-air missile.
However, in the absence of any concrete admission of guilt, the internet has come to up with its own ideas – some more outlandish than others. Here are just some of the conspiracy theories:
New World Order launches World War III
Before It's News found it suspicious that the Ukrainian government knew exactly what had happened to flight MH17 just minutes after the crash. This fact, when combined with the "convenient" discovery of dozens of "pristine" Malaysian passports at the crash site proved that the incident was an attempt by the New World Order (NWO) to trigger a third world war, it claimed.
For those unfamiliar with the group, the NWO is a shadowy power elite that is conspiring to rule the world. The Machiavellian group needed to provoke a global war, said Before It's News, because the US dollar was in trouble and its grip on power was in danger of collapsing.
Nato wanted to assassinate Putin
Pravda, once the official newspaper of the Communist Party, published a story entitled "MH17: some conclusions - did Nato try to murder Putin?" The article alleges that Russian president Vladimir Putin was believed to be flying the same route as MH17 at the very same time, and that the Russian president's aircraft has "very similar contours and colouring". It is therefore likely that the missile that struck the MH17 was an attempt to take down Putin's plane, said columnist Timothy Bancroft-Hinchey. "After Iraq, after Libya, after Syria, would anyone seriously rule out a Nato attempt to murder President Putin?" he asks.
An auspicious date, a recurring number
Malaysia Airlines Flight MH17, a Boeing 777, made its first flight on 17 July 1997, 17 years to the day before it crashed, noted CJ Chivers of the New York Times' in a tweet.
The proliferation of sevens did not escape the attention of some other conspiracy theorists, including Glaswegian truth-seeker, Kev Baker, who suggests that when considered together, the date, time and flight number indicate foul play.
Israel hoped to divert attention from Gaza
Some speculate that the downing of MH17 may have been an attempt by the Israeli government to divert attention from its ground operations in Gaza. Media with Conscience reports that the missile was launched by agents of the "US, Apartheid Israel, EU, Australia and neo-Nazi-backed Ukrainian Government" which has been "the only beneficiary from the MH17 atrocity and a key suspect" in the crash.
It was Illuminati, not aliens
"I followed the previous Malaysia Airlines Flight MH370 (exhaustively) and concluded that it must've been aliens; one of the first conspiracy theories to surface, and until we hear otherwise I'm sticking with it," said the writer. "In that MH370 conspiracy theories post I referenced the fact that the alleged Illuminati might have been involved due to the number 777 being tied in. You'll notice that this MH17 was also a Boeing 777."
A bid to conceal the true origins of HIV/Aids
Several prominent HIV/AIDS researchers died on the flight, prompting some theorists to suggest that the attack was a cover-up for the "man-made origins" of AIDS.
They can't all be wrong
Purveyors of conspiracy theories have at least four powerful motives, argues Patrick Cockburn in The Independent. These include a "natural human delight" in complicating matters and telling a good story; proving that an enemy is "not only bad but demonically cunning"; making money; and that a proportion of them are true. For all the ludicrous theories that exist, Cockburn concludes, there are also some real conspiracies out there.
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