According to the flight plan seen by researchers, the aircraft was chartered by Hong Kong-based Union Top Management Ltd., or UTM, to fly oil industry spare parts from Pyongyang to Tehran, with several other stops, including in Azerbaijan and Ukraine.
Thai authorities, acting on a U.S. tip, impounded the Ilyushin Il-76 cargo plane when it made a scheduled refueling stop in Bangkok on Dec. 12, uncovering 35 tons of weapons, reportedly including explosives, rocket-propelled grenades and components for surface-to-air missiles. The plane's papers described its cargo as oil-drilling machinery for delivery to Sri Lanka.
The U.N. imposed sanctions in June banning North Korea from exporting any arms after the communist regime conducted a nuclear test and test-fired missiles. Impoverished North Korea is believed to earn hundreds of millions of dollars every year by selling missiles, missile parts and other weapons to countries such as Iran, Syria and Myanmar.
The report on the flight plan from the nonprofit groups TransArms in the United States and IPIS of Belgium was funded by the Belgian government and Amnesty International. It could not be independently verified.
The report says the plane was registered to Air West, a cargo transport company in the former Soviet republic of Georgia. Asked to comment on whether the plane was bound for Tehran, company owner Levan Kakabadze told The Associated Press that he was unaware of the plane's final destination.
Speaking by telephone from Batumi, Georgia, Kakabadze said that he had leased the plane to the SP Trading company and could bear no responsibility for what happened next.
"I know that the flight documents listed the cargo as oil drilling equipment. It turned out that they were carrying weapons," Kakabadze said. "After leasing the plane, I can't be held responsible for what happened. It's a problem for people who leased the plane. I have nothing else to say."
The authors cite confidential e-mails saying that UTM had ruled out a direct flight from Pyongyang to Tehran.
The report also raises multiple questions, including why the plane would stop in Thailand, since arms traffickers would be wiser to fly over China toward the former Soviet republics and on to Iran, rather than the well-policed southeastern Asian country.
It says that the final flight plan shows that the aircraft stopped at an Azerbaijani air force base a few miles (kilometers) north of the capital, Baku, on its way to North Korea, and was expected to make a stop there on its way back from Pyongyang to Tehran.
An Azerbaijani aviation spokesman Tuesday denied the plane stopped in his country, which shares a border with neighboring Iran.
"The claims that the plane made a refueling stop in Azerbaijan have nothing to do with reality," said Maharram Safarli, a spokesman for the national flag carrier AZAL. "This plane has never landed in Azerbaijan."
The report, which was released Monday, also says that the aircraft's lease owner, SP Trading, which is located in New Zealand, was told that the equipment on board should be brought to Ukraine first for handling before its delivery to Pyongyang.
Ukrainian Foreign Minister Petr Poroshenko has been quoted as saying that the plane was not Ukrainian. He said the plane landed in Ukraine on Nov. 13 empty and left empty on Dec. 8.
The researchers say that the plane's previous registration documents link it to Air Cess and Centrafrican Airlines, which are allegedly connected to accused weapons trafficker Victor Bout, who has been in prison in Thailand since he was arrested March 6 and is battling attempts to be extradited to the United States on terrorism charges.
But, the report said there was not enough evidence to link the plan definitively to Bout.
"In the arcane and esoteric world of former Soviet aircraft registration it is only possible to say that it is 'highly probable' that this aircraft is the same plane which, up to a decade or so ago, was part of a fleet of aircraft which 'quite likely' were under the control of Mr. Bout," it said.
"But this is rather like saying that possession of one's vintage Jaguar, which a decade ago was used as the getaway car in a bank job, makes one a bank robber."
The aircraft itself was formerly a Soviet air force plane that was later converted to civilian use in Ukraine before it was reportedly exported to Malaysia in 1997. It resurfaced in Swaziland in 1998 and was spotted again in the United Arab Emirates in 2003.