The pilot of MH17 radioed that he 'felt uncomfortable' about the route he was flying while over Ukraine and tragically altered his course to hostile territory, according to an expert.
Dr Igor Sutyagin, Research Fellow in Russian Studies from the Royal United Services Institute, believes that MH17 was shot down by rebels based in the 3rd District of Torez, in eastern Ukraine, after mistaking his plane for a government military transport aircraft.
He told MailOnline that information had been leaked from a source he was unwilling to name that the pilot of MH17 'felt bad' about his course over Ukrainian airspace, so changed direction.
Little did he know, according to Dr Sutyagin, that his plane would then be mistaken by rebels who brought it down using a ground-to-air Buk missile system.
His theory appears to be supported by a route map which shows the passenger plane travelling on a different course to the ones taken by the previous ten MH17 flights.
Twitter user Vagelis Karmiros collated the information from Flightaware, the largest flight tracking website in the world.
He said: 'There is a Ukrainian mechanised brigade blocked by separatists near the Russian border.
'It's blocked on three sides by separatists and behind the brigade is the Russian boarder, so they can't get out. The Ukrainians try to resupply them from the air by transport aircraft.
'Now, the pilot of MH17 said that he "felt bad" and wanted to change course south to get out of the danger zone. But several kilometers to the south is a Ukrainian Army heavy transport plane, an IL76, or Candid, which has the same echo as a 777 on a radar screen.
'The two planes came close. They tried to shoot down the transport delivering supplies to the brigade. They believed that they had been firing at a military plane, but they mistakenly shoot down a civilian airliner.'
Rescue workers, police and even coal miners are today combing the site where a Malaysian Airlines jet crashed after being shot from the sky by a surface-to-air missile, scattering wreckage and bodies across the Ukrainian countryside.
Ukraine accused pro-Russian separatists of shooting down the plane which was flying from Amsterdam to Kuala Lumpur with 298 people on board, while the Russian media today blamed everyone but pro-Moscow rebels for the Malaysia Airlines horror.
One theory explored by TV and newspapers was that the Ukrainian armed forces may have shot the Boeing out of the sky after mistaking it for Vladimir Putin's official Ilyushin jet.
The Kremlin leader was flying back to Moscow from Brazil at around the same time that the Boeing 777 was downed, stated TV and newspaper reports.
Evidence for the theory seems scant, but an anonymous source in Russia's Federal Agency for Air Transportation was quoted saying that there was a crossover flight path between the doomed Malaysian aircraft and Russian plane 'number one' used by Putin.
A source at the agency was quoted by Komsomolskaya Pravda newspaper as saying: 'Vladimir Putin's plane could have been a target for a Ukrainian missile.'
NTV cited a source from the same body as saying: 'I can say that the routes of plane Number One and the Malaysian Boeing crossed at the same point and on the same altitude.
'It was near Warsaw at altitude 10,100 metres, echelon 330. The plane Number One was at that point at 16.21 Moscow time, the Malaysian plane was there at 15.44 Moscow time.'
The source also said that the 'plane' contours are similar in principle, the real sizes are also similar, and 'as for their liveries then at the distance they are almost identical'.
Putin's equivalent of Air Force One is a specially modified Ilyushin, the Il-96 300. It is a four-engine long distance aircraft, with a length of 55 metres, and a wingspan of 60 metres.
The Boeing 777-200 is 63 metres long, and its wingspan 61 metres.
Asked last night on the route of Putin's plane, agency head Alexander Neradko said: 'We never comment on the routes and other details of the flights of the president of Russia.'
Earlier, Ukrainian government official Anton Gerashchenko accused Mr Putin of 'a desperate attempt to hide the consequences of his deeds' by permitting the smuggling of the Buk rocket launcher - suspected of being used to shoot down the Boeing - across the frontier into Russia.
An effort during the night was made 'to hide the Buk rocket complex on Russian territory', he alleged.
He did not say if it was known whether or not it had moved into Russia.
'It is most likely that the machinery which fired the missiles at Malaysian aircraft will be destroyed and the people who committed the act of terror will be annihilated,' warned Gerashchenko, an advisor to the Interior Ministry in Kiev.
'Several hours ago, Putin made a statement in regard the catastrophic crash of the Malaysian Boeing in which he blamed it all on Ukrainian side. What else is there to be done for an international terrorist? Only lie.'
Meanwhile, Pro-Kremlin Izvestia cited separatists claiming the shooting out of the sky was 'a planned provocation by Kiev'.
'Judge for yourself, who could have done it? The rebels don't have weapons that you could use to shoot down a plane at such a height, but Kiev does,' one local leader told the paper.
Tabloid Tvoi Den splashed a full-page cover photograph of the crash scene with a line reading: 'Donetsk People's Republic Authorities Claim Plane Destroyed by Ukrainian Buk Missile,' an anti-aircraft system.
Rebel official Sergei Kavtaradze was quoted saying: 'According to our information, this plane was shot down by Ukrainian armed forces.'
Other media claimed it could have been a Ukrainian plot to give the Americans an excuse to deploy NATO on the ground in the eastern European country.
But a Ukrainian military expert, Igor Levchenko, told Kommersant business daily that although Kiev did have several Buks in the conflict zone, they 'definitely would not be used against such a target as a passenger liner.'
Turning some of the blame towards the aviation industry, the same paper cited aviation sources saying it was 'reckless' to allow passenger flights over the region.
Government newspaper Rossiiskaya Gazeta said: 'It remains unclear how a Boeing 777 came to be above a conflict zone and why air traffic controllers didn't prevent a potentially dangerous situation.
Malaysia's transport minister today insisted there were no last-minute instructions to the pilots of MH17 before it took off.
Liow Tiong Lai said the Boeing 777 was flying on an internationally-approved route which other airlines had been using 'in the hours before the incident'.
He said: 'Our sympathies are with those affected by this tragedy. There were 298 passengers and crew. Our thoughts and prayers are with the families at this incredibly difficult time for them.'
Mr Lai reiterated that the plane had 'a clean bill of health' and all its systems were functioning normally.
The route taken over Ukraine was one approved by the International Civil Aviation Authority and by the International Air Transport Association.
He went on: 'There were no last-minute instructions given to the pilots to change the route. In the hours before the incident, a number of airlines used this route.'
Mr Lai said that of the 41 passengers whose nationalities were initially unknown, 21 had now been identified.
Listing the nationalities, he confirmed that nine UK passengers were among those lost.
He added that the full passenger manifesto would be released once all next of kin had been informed.
Mr Lai called for the crash site to be preserved, adding that Malaysia was sending a dozens-strong team to Ukraine, which would include 15 medical staff.?Malaysia Airlines is also sending 40 staff to Amsterdam to support families there.
Speaking at a media conference in Kuala Lumpur, Mr Lai said Ukraine would start the investigation into the crash and he supported a call for an international investigation.
The Duke of Cambridge spoke today of his 'deep sadness' over the Ukraine plane disaster.
Speaking at an event at Australia House in London to remember a British explorer, William said words 'cannot do justice to our sense of loss'.
Prime Minister David Cameron said the crash of Malaysia Airlines Flight MH17 in Ukraine was 'an absolutely appalling, shocking, horrific incident' and said his thoughts were with the families of those killed.
Mr Cameron said: 'If, as seems possible, this was brought down, then those responsible must be held to account and we must lose no time in doing that.'
Off-duty coal miners joined the search effort early today in fields near the rebel-held village of Hrabove in the Donetsk region of eastern Ukraine, about 25 miles (40km) from the Russian border, where fighting has raged for months.
Large chunks of the Boeing 777 that bore the airline's red, white and blue markings lay strewn over a field.
The cockpit and one of the turbines lay more than half a mile (1km) apart and residents said the tail landed about six miles (10km) away, indicating that the aircraft probably broke up before hitting the ground.
Bodies and body parts strewn across the field outside the village of Rozsypne about 2.5 miles (4km) away from the crash site.
American intelligence authorities believe a surface-to-air missile brought the plane down but are still working on who fired the missile and whether it came from the Russian or Ukrainian side of the border, a U.S. official said.
Malaysia's prime minister said there was no distress call before the plane went down and that the flight route was declared safe by the International Civil Aviation Organisation.
More than half of the passengers on board - 154 - were Dutch citizens, with 43 from Malaysia, including the 15 crew members.
Another 27 were Australians, 12 from Indonesia, and nine Britons. The victims included three infants.
Earlier it was feared that 23 Americans had perished based on a Reuters report, but there has been no confirmation of any U.S. deaths since then from the State Department.
Ukrainian President Petro Poroshenko called it an 'act of terrorism' and demanded an international investigation. He insisted his forces did not shoot down the plane.
U.S. Senator John McCain said there 'would be hell to pay' if the plane was shot down by the Russian military or separatists.
Earlier this week, the rebels claimed responsibility for shooting down two Ukrainian military planes.
In Kuala Lumpur, several relatives of those on board the jet gathered at the international airport.
A distraught Akmar Mohamad Noor, 67, said her older sister was coming to visit the family for the first time in five years.
'She called me just before she boarded the plane and said, "See you soon",' she said.
Counsellors were meeting with a few family members in the airport viewing gallery, sealed off from a horde of journalists. One woman emerged in tears and was escorted out of the airport by a security officer without saying anything.
'This is just too much,' said Cindy Tan, who was waiting at the airport for a friend on another flight.
'I don't know really why this happened to a MAS (Malaysia Airlines) plane again.'
Ukraine's security services produced what they said were two intercepted telephone conversations that showed rebels were responsible.
In the first call, the security services said, rebel commander Igor Bezler tells a Russian military intelligence officer that rebel forces shot down a plane.
In the second, two rebel fighters - one of them at the crash scene - say the rocket attack was carried out by a unit of insurgents about 15 miles (25km) north of the site.