Flight 182 was on its way from Montreal to Delhi when it exploded over the Atlantic Ocean on June 23, 1985. Most of the victims were Canadian citizens.
Two of the accused Ripudaman Singh Malik (56) and Ajaib Singh Bagri (53) sat in the court behind a bulletproof glass, while a third Inderjit Singh Reyat is serving a jail sentence after pleading guilty for manslaughter.
Malik and Bagri, arrested in October 2000, are both prominent members of Western Canada's large Sikh community. On Monday, they pleaded innocence.
The prosecution's case rests on circumstantial evidence, based largely on statements they allegedly made to a handful of witnesses in the years after the bombing.
Prosecutor Robert Wright told the court that Malik and Bagri were 'terrorists' so driven by a need for revenge (for the storming of the Golden Temple in 1984) they were willing to kill 'hundreds of innocent people'.
The duo was allegedly part of a group of Vancouver-based Sikh militants who conspired to destroy two Air-India jets simultaneously at opposite ends of the globe.
The explosion of Flight 182 was the deadliest act of sabotage in aviation history until the September 11, 2001, attacks (in the US).
Malik, 56, a wealthy Vancouver businessman, and Bagri, 53, a Kamloops, British Columbia, sawmill worker, are also accused in an explosion in Tokyo's Narita airport, which killed two baggage handlers.
The bomb was in luggage that was to being transferred to another Air-India flight.
Malik's and Bagri's legal teams, who are working independently in the trial, which is being heard by a single judge, both attacked the credibility of the prosecution's witnesses.
They said witnesses were only repeating rumours widely reported by the media after Flight 182 was destroyed.
Malik's attorney, David Crossin, said the key witness against his client was motivated by revenge because she was a former employee who had been fired. Mediapersons are banned from naming the witnesses by a court order.
Crossin opened his statement by acknowledging that the destruction of Flight 182 was a 'horror', but said it was important for his client to receive a fair trial.
"Even if there was a conspiracy, Bagri was not a member," his lawyer Richard Peck said in his opening remarks.
About two dozen relatives of the victims were in the courtroom, and said they were relieved the trial was finally getting under way.
Members of Malik's and Bagri's family were also in the court, but sat on the opposite side of the room in the high-security facility specially build for the trial.
Majar Sandhu of Vancouver heard in court for the first time that Malik allegedly talked to his sister, niece and nephew several days before Flight 182 exploded, and although he knew they were going to be on the aircraft he did not warn them.
"Incredible," he said outside the courtroom, adding that he was confident the men would be convicted.
Prosecutors confirmed on Monday that they would also call Reyat and his wife as witnesses. Reyat pleaded guilty in February to a lesser charge of manslaughter -- buying the materials used to make the Flight 182 bomb.
Prosecutors and defence attorneys also confirmed on Monday that they had reached a deal to admit large amounts of technical evidence about that bombing without arguments, which will reduce the amount of witnesses called.
Even on the speedier time table, the trial is not expected to end until early 2004.
Among the evidence presented on Monday was that the X-ray machine used to screen baggage loaded on the doomed Flight 182 aircraft was not working, and the replacement system to detect explosives was unreliable.
The bags that contained both the Flight 182 and Narita bombs belonged to male passengers who purchased one-way tickets in cash, using false names. They never boarded the aircraft.
Reuters